Grace Design m9XX compact USB DAC with integrated headphone amp


100+ Head-Fier
Pros: Small footprint, crossfeed is well done, detailed yet fun
Cons: Strange hum when muted, still white noise on sensitivce iem's (minimal)
Grace Design m9XX Review
Where I say stuff that you may want to know about myself and my music preferences
There is already many very well done reviews of this product already here on Head-Fi, so I will try and not belabor my points to much for this review, but you may need to put up with a little of my grandiloquence at times! (Got to keep it interesting right?)
First off I would like to describe my music preferences.  I think this is an important thing to consider while reading reviews as sound preferences are very unique and personal.  I tend to enjoy a more neutral to warm sound, however I do not like extremely rolled off treble.  I need a little sparkle in my headphones or they just sound boring and bland.  My current favorites are the SRH 1540’s.  They have slightly elevated bass and a wonderful treble extension. 
I listen to just about every music genre.  I mostly listen to classical, singer song-writer, scores and electronic/dance.  Yes I do realize those are both large, and widely varying categories.  Point being I listen to many types and styles of music. 
Full sized headphones used to assess the m9XX were the Shure SRH 1540, Beyerdynamic DT 990 pro (250ohm), and the Beyerdynamic T70p.  IEM’s used were the Shure se215, Thinksound Rain2, and RHA s500i.
Overview for m9XX:
Get to know the m9XX on a more personal level
This is one solid piece of hardware.  Prior to the m9XX I used the Fiio e17+ e09k combo for my desktop.  One excellent thing about the m9XX is that it has such a small form factor.  It really takes up less space than my Fiio, which is impressive as that is pretty small already as far as desktop units are concerned.  It is very sturdily built.  It has a good heft in the hand and certainly gives the feel of being premium. 
The m9XX contains two USB inputs.  One has a dual purpose of providing both power (low only) and data transfer.  The second is strictly for power.  Plugging in the second cable enables High Power Mode which will allow you to drive most headphones.  In addition to supporting USB audio (both class 1 and 2). You can opt to use the Toslink input as well.  Finally it features an RCA out allowing you to either connect another amp of your choosing, or to connect to active speakers (will not drive passive speakers). 
Moving to the front of the unit you will find two ¼ jacks for a headphone of your choosing.  It is nice to have the option of two in case you wish to share with a friend, or perform quick A/B comparisons of different headphones.  Additionally, you will find a small 2 digit display.  This little display will tell you all you need to know about what, and how the m9XX is functioning.  I was very impressed with how simple the interface was, so kudos to Grace Design and Massdrop for designing an excellent interface.
The owner’s manual is a wealth of information so I will leave a link for your reading pleasure!
Here is another link to other, more in-depth information for the m9XX.  You will need to copy and past it, as it wont allow me to create a link for some odd reason.
Listen to that music!
If I had to describe the sound characteristics of this device I would say it is near neutral with excellent clarity and refinement.  Distortion is noticeably lower than my old Fiio set-up.  It definitely smooth’s the upper treble a bit, which dramatically decreases some grain found in some tracks.  Furthermore it has a nice tight bass response.  It is very noticeable on the SRH 1540 which can occasionally suffer from bass bloat in the mids.  This has been reduce and has strengthened the overall clarity.  Overall it has a wonderful, easy to like sound signature.  Having said this it may not pair well with certain headphones according to some reviewers, but I cannot comment on this as it seems pair well with all of my cans. 
There are two other important features about this device’s sound.  The first being the filters.  Grace Design describes the filters like this:
“DAC FILTER Changes the response of the digital filter. Push and release the encoder to scroll through the filter response modes:
 F1 = sharp roll off, linear phase
For linear phase response and time coherency. Fast roll off protects against aliasing distortion from high amplitude high frequency content.  Best for recordings that are loud, compressed, and with lots of treble. Will contain substantial ringing before and after transients (pre-echo and post-echo). Note that the ringing occurs at the Nyquist frequency (½ of the sample rate), so it is not directly audible. However, it can cause intermodulation distortion in downstream components.
 F2 = slow roll off, linear phase
For linear phase response and time coherency. Best for acoustic music without compression and artificially high levels of treble. Will have very low levels of ringing before and after transients but is susceptible to distortion artifacts caused by high amplitude high frequency information in the program material.
 F3 = sharp roll off, minimum phase
Not linear phase in the pass band. Fast roll off protects against aliasing distortion from high amplitude high frequency content. Best for recordings that are loud, compressed, and with lots of treble. Will contain substantial ringing caused by transients, but all of the ringing is shifted to after the transient. This can reduce the perceived effects off downstream intermodulation distortion due to the Hass Effect.
 F4 = slow roll off, minimum phase
Not linear phase in the pass band.  Best for acoustic music without compression and artificially high levels of treble.  Will have very low level of ringing caused by transients and ringing will be shifted to after the transient.”
Truthfully they all sound very similar and I was not able to tell much difference between all of the filters.  I decided to leave it at F1.  It paired best with my SRH 1540’s simply because it smoothed the notorious treble spike it has.  I do think the name is misleading however.  The name “Sharp roll off” seems to imply that the treble is going to drop off the face of the earth and be non-existent.  This is not true.  Instead it is simply smoothed and given less edge.  This was also helpful for my T70ps as they are exceedingly bright at times.
The second aspect that I really find myself enjoying is the crossfeed feature.  Some of you may be wondering “what the heck is crossfeed?” Crossfeed is really an ingenious way to help eliminate the polarization that occurs while listening to music through headphones.  When you listen to music through speakers both of your ears hear the music, but one ear hears the signal a little louder than the other (the one that is closest to the source).  Using these varying signal inputs your brain can calculate the special awareness of the music in the room.  By applying crossfeed you enable a similar effect, but with your headphones.  It is employed very well and truly does make for a much more natural listening experience.  Most noticeable changes are: Increased sound stage, better separation, and better imaging.  The only drawback is it has the potential to suck the mids out a bit.  This is only a problem with extremely U shaped headphones, like the DT 990.  With crossfeed on the mids were sucked way out, making vocals sound faint and muffled.  In contrast both the Shure 1540’s and T70p’s (both more midcentric) sound sublime with crossfeed enabled.
Better than the energy drink!
I won’t talk too long about the amp section, as they are not an area I feel well versed in, and there is much discussion already here on Head-Fi in the forum.  What I can say is that it powers all of my headphones exceedingly well and has a velvety black noise floor thanks to the ultra-low output of 0.08 ohms. This includes sensitive IEM’s as well, although there is white noise present, it is very negligible and not noticeable at all while music is playing.
Meant for a desk? Or for the road
This device is certainly compact.  Because of this compactness many have decided to use it as an on-the-go companion.  For me personally it is not a viable simply because I have other portable options that are far more compact (Fiio K1).  While they do not offer nearly the level of audio quality that the m9XX offers, I am willing to sacrifice for more portability. 
Having said this, the m9XX can certainly be used as a portable.  This is because of the ability for it to be driven without a power adapter.  This does limit you slightly as hard to drive headphones will not work as well, however these types of headphones are rarely used as portables.  So, if you are looking for an al-in-one solution for both a desktop, portable, and was the best from your music the m9XX should certainly be on your short list.  It is essentially a far more portable version of the Schiit Bifrost. I do want to clarify though, I have never personally heard the Bifrost.  I make this statement for a few reasons.  One it has the same chipset so this would mean they may have similar characteristics (although this is not always true).  Secondly, I make this statement based on several other users stating they have similar, albeit different characteristics when it comes to quality.
Weaknesses of the m9XX
Everything has a weakness…
Over my course of having the m9XX I have really only found one weakness that I truly do dislike.  The easy mute feature is nice as it allows the user to quickly silence the music.  What I noticed, while testing with my t70p and with my IEM’s was that there is an audible hum noise (almost like interference) when initially pressed.  What is more interesting is that this humming disappears once the screen is dimmed, assuming that feature is enabled.  If it is not enabled than the hum persists until the music resumes being played.  What is concerning is that it seems directly tied to the display, which means it is potentially causing interference any time it is on.  I have yet to read anyone else having this issue so it is possible that it is strictly my device.
Luckily, however, it does not seem to affect the music whilst it is playing, as I tested this with quiet tracks.  I cranked the volume and there was no hum until muted.  My thought is that the hum is somehow tied into the mechanism that causes the screen to pulsate, indicating the music is muted. 
I contacted Grace Design about this issue and the told me this:
  When the device is muted, the display uses a PWM scheme to make the screen pulse. The noise you are hearing is a by-product of this. This noise is usually only heard on very sensitive headphones like IEMs. When the unit is un-muted, there should be no noise caused by the display. This is normal behavior and should not be cause for concern. Please let me know if you have any questions!

Final Verdict
So what do I think?
I personally think this is an amazing device.  Given its price point it is both an investment, but also a bargain.  The only real improvement a person could make would be in the amp.  This is truly only necessary if you have hard to drive headphones (above 300 ohms).  It has wonderful music separation and greatly reduces distortion in the upper treble region.  It will also tighten up the bass response allowing for a nice, tight, impact.  It has been known not to pair well with some headphones, but for me it pairs well with all of my headphones, so long as I take crossfeed off when listening to the DT 990’s.  All I can ultimately say is: Well done Grace Design and Massdrop for bringing a wonderful device to the audiophile community!
Questions? Comments? Please let me know!


New Head-Fier
Pros: Compact, somewhat portable, incredible sound, and for $499.99, it might even best some of the $1500+ DAC's out on the market.
Cons: Only 500 units from Massdrop, and only one drop so far. Relatively new, so limited reviews.
This is my first user review, and I just got the unit a few hours ago, so I'm keeping it short for now, and I'll update more later.




The Grace Design m920 came in a few hours ago. I'll probably end up writing more as the days go by.


Switching between my Grace Design M920 (24-bit 196kHz), M9XX, (32-bit 192kHz) and SMSL M8 (32-bit 192kHz, paired with an Objective 2 amp). The SMSL M8 for the $149.99 drop, is decent, but still doesn't compare to the Grace Design M920 and M9XX. I prefer my digital filters with a Slow roll off (linear phase). With this digital filter setting, the SMSL M8 won't go slow enough for my tastes. Listen to any acoustic vocals song, and you'll notice the difference. The M920 and M9XX handles it very well.


Currently, I'm comparing with my AKG K7XX at level 72 (and for the Objective 2, getting it close to that level as far as I can tell). I'll be switching to different headphones to test even more.


I am really trying hard to find the differences between the M920 and M9XX, but they are so subtle, it's difficult to pinpoint. Listening to Yo-Yo Ma's Cello Suite No. 1 in G Major (via Tidal HIFI), starting at the 1:52 minute mark, the crescendo and drop off actually sounds better with the M9XX than the M920. Yeah, weird, right?

I'm starting to feel a little bummed that I dropped $1500 on the M920, lol. I'll need to keep listening to different types of music so I can feel better about having the M920 over the M9XX.
Asking around the forums for anyone that had both the M920 and M9XX, I came across the same sentiment, and I was able to pinpoint in more detail the difference between the M920 and M9XX.
Listening to "Serve the Ego" by Jewel (via Tidal HIFI), starting at 0:09 and ending at 0:14, you can definitely hear a difference. The M920's lows resonates a bit deeper. I mean, I really, really had to listen to it over, and over. Switching between the F2 and F4 digital filters on the M9XX, I wasn't able to discern any noticeable differences between the two settings.
Which makes sense as to why Yo-Yo Ma's Cello Suite No. 1 in G Major the day before sounded better with the M9XX. A faster paced routine like that is going to sound better with the M9XX, but something slower paced, the M920 will resonate much deeper into your soul.
To be continued...
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looking forward to your updates, please post asap!


Headphoneus Supremus
Pros: DAC transparency; ultra-low-impedance amp; neutral, flat, clean sound; crossfeed; DAC filters; build quality; form factor is small and well designed
Cons: won't drive the most demanding headphones properly (HE-6, 600 Ohm beyerdynamics, etc); can only buy through massdrop
In the last year, I changed my approach to headphone setups.  At one point I had a desktop setup for the HD650 (Bifrost + Lyr), a mobile amp with various portable cans I've owned (various FiiO products), and a small, work setup (Modi+Magni stack) for my Shure SRH840.  What I realized is that a large portion of the time I was not using any of that stuff and i was often simply using my Grados or KSC75s through my iPhone because it's convenient and I could do chores around the house or walk the dog.  I was spending a majority of my time with my least expensive setups.  
So I decided to simplify based on a few rules:
1) Any headphones had to be drivable by an iPhone and sound very good straight out.
2) All gear had to be all-arounders, in that it sounded good with any gear I own, and all amps work well with all headphones.  No more of this "this amp is for this headphone" stuff.
3) No more big desktop stacks.
But I also didn't want to compromise on audio quality either.  I was unsure if this was possible, but I wanted to see how close I could get.  So, I first sold off all the gear that didn't fit that program.  HD650, all my Schiit gear, gone.  
Headphones were the next big decision.  First move was the Shure SRH840.  To me, that's the best closed headphone in the $200 range (yeah, better than the M50X).  Grado SR225e came next as my fun, open can.  Then I demo'd the HiFiMan HE400i and knew that would be the cornerstone primary headphone.  
The next challenge became the DAC/Amp.  While everything had to be drivable by the iPhone, I did want something that I could use to take them to the next level.  And that was surprisingly challenging.  
People on here often talk about "scaling well" and primarily what they mean is that the headphones are hard to drive, and thus require an expensive powerful amp to properly power.  In my experience, easy to drive headphones can actually be more challenging to properly power.  Lower impedance easy to drive headphones require a lot of current, rather than a lot of pure power.  You also need a low output impedance for dampening.  The 02 was one of the first amps to really "get" this.  But it was shrill to my ears with a lot of headphones.  The Schiit Magni also offered this, but again, I didn't want a stack.  
I had always been drawn to Grace units, but A) they were the size of a rack unit and B) they were $1500-$2000, which was more than I wanted to spend.  
Things started to come together when I saw the announcement for the m9XX.
The m9XX on paper looked about perfect.  
The ultra-low impedance meant that it would drive a lot of current (ohms law states that as the output impedance goes toward 0, current goes towards infinity), especially since it could deliver 1000mW at 32 ohms. With an output impedance of 0.08, this meant that the current it sent to headphones was literally near infinite.  
The design was spot on: simple, ergonomically appealing, attractive.  It had several features I found very appealing as well:
1) Crossfeed.  To me crossfeed is nearly required for long listening sessions to avoid fatigue.  Without it, it's like my brain gets tired trying to reconcile hearing sounds consistently only out of one ear (this almost never happens in real life, so it confuses your brain).  
2) linear decibel stepped volume control.  Most amps have a volume control where power levels are just some arbitrary points. often times halfway through the dial isn't half power, or half volume or anything in particular.  On the Grace m9XX, each spot represents an actual half decibel.  This makes it possible to fine tune adjust the volume on an IEM and a planar magnetic headphone without using a gain switch (and thus changing the output impedance as well).  It also makes it very easy to understand volume differences, since the display numbers are actual decibels.  
3) one output line that allows the RCA outs to still work, and one that mutes the RCA outputs.  This allows a number of things: you can play two headphones at the same time, for quick critical comparisons (or listening with a friend), using a sub with your headphone (try it, it's an interesting experience) and auto-muting speakers you may have been feeding from the DAC.
4) ability to be both USB powered, but also have a high power mode that doesn't change the gain (and thus maintains the low output impedance) but adds more headroom.  For many headphones USB bus power is all you need, but it's nice to have that little extra power you can send if needed, and unlike gain switches, it doesn't make things more noisy, or add impedance.  
5) The DAC chip was the same as the DAC chip in my bifrost, which even though I wanted to slim down the form factor, I loved the sound of the bifrost.
That all looked great on paper, and combined with Grace's reputation, I decided to jump in.  Even if the amp was merely decent, $499 was a reasonable price for the DAC, given the components and features.  
So, I got it; did it live up to my hopes/expectations? (well, spoiler alert if you noticed the rating I gave, you know the answer to this)  
Yes, absolutely it fulfilled my expectations, 100% and then some.  

First, the build quality, fit, finish and feel exceeded my high expectations.  Supposedly the engineers at BMW exhaustively test each car, so that the sound and feel of the door closing is just right.  That's how the volume control feels when you turn it or push it down (push to mute or hold to access the settings menu).  The front, back and top plate is one piece of high quality aluminum.  It feels solid without being heavy.  It manages to seem both robust yet elegant.  
It's the apple macbook pro or BMW 5 series of audio equipment.  Fit, finish, feel and performance all coming together perfectly.
Now, on to the sound part:
It manages to be incredibly transparent, spacious, with great treble and bass extension, without sounding dry and brittle.  It's extremely transparent, yet musical.  Nothing about it sounds unnatural.  It just gets out of the way, and takes on the character of the headphones and music instead of imparting its own footprint.  This isn't what you want, if you want to hear your DAC/amp in your chain.  You don't hear the m9XX, you hear *through* the m9XX.  You'll instead hear your music and headphones.  To me, that's the ultimate compliment for a DAC/amp, that it simply gets out of the way and lets everything else do its part.  
Now, coming back to what I said at the beginning, where this amp really shines is on lower impedance headphones.  It can drive an HD650 very well, but to me, in some ways, driving low impedance headphones has its own challenge.  Most of the headphones I own are very current hungry, that is, instead of needing a lot of absolute power, they need a lot of current to tighten up and define the bass, and refine the treble and midrange, and give shape and definition to the soundstage and accuracy to the imaging.  This is the real key to the m9XX, that it can make your low impedance headphones sound like you've never heard them before.  And it can drive IEMs well.  And it can even sound really good on a freaking HD800.  0.08 output resistance with 1mW of power makes this ultra versatile.  
High Power Mode is vastly superior to most amps High Gain Mode: more current, less noise, no increase in output impedance
Talking a bit more about how high power mode works, and why it's substantially superior to the "high gain" mode of most headphones: In high power mode, instead of increasing the gain, Grace simply adds more headroom.  You'll notice that 70 on low and high gain are the same loudness.  You don't get an increase in noise at all, like you do with most DACs high gain mode, you don't get an increase in output impedance.  You do get more current, which most amps high gain mode don't actually send more current, they just increase output impedance.  Basically High Power Mode adds headroom and the ability to use settings over 90 without running out of current on tap and getting a "OC" (Over Current) error and the consequent muting.  
Now on to how it sounds with various headphone pairings I tried it with.
With the HiFiMan HE400i, the pair is just effortlessly balanced and precise.  
I think the HE400i paired with the Grace m9XX could be my endgame setup.  As they've both rolled past 150 hours, with 80 hours of "on head" time, this is just such an incredible pairing.  
Ihis is the *perfect* pairing for long sessions.  Enabling crossfeed on the Grace, and this is the least fatiguing headphone I've ever heard.  The resolution and transparency means that I never have to strain to hear anything.  The tonal balance, flat bass and  (to me) neutrality means no frequency ever wears you out. The crossfeed makes for a less fatiguing listen as well.  While the soundstage isn't vast on the HE400i, it's so coherent and imaging is so precise, that it's an effortless listen.  It's present without being sibilant.  The bass is full and extends, without booming (which can get fatiguing after a while to me).  
The signature, right away, can almost seem boring.  But it's just so resolving, transparent and fast, while being smooth and musical, that those qualities become fun in their own right.  I realize instead of being like "wow, oh my god the bass" like I am with some equipment, more often I think "wow, this song is incredible."  WIth this pairing it just becomes so squarely about the music as opposed to noticing things about the headphone, amp and DAC.  
The word that keeps coming to mind with this pair is simply "effortless" They just effortlessly bring me my music.  They get out of the way.
Finally this pairing has by far the most listenable range of volume I've ever heard.  On the Grace, I find the HE400i listenable from 59 to 79.  That's 20 dB of difference that I find them perfectly listenable.
With the Fostex THX00, the pair is rich, smooth, detailed and powerful
The THX00, like the other TH series cans, and the old Denon DX000 predecessors are tricky to amp, despite not needing much in the way of absolute power.  They're very easy to drive, but if they don't get a lot of current, the bass can be quite uncontrolled, especially on hard fast bass transients.  The Grace comes in and cleans this all up with aplomb.  A can that out of other amps can sound average in terms of detail and imaging becomes quite good in those areas.  To my ears the Grace gives these cans exactly what they need, a very resolving and spacious DAC and tons of current because of the Grace's ultra low output impedance in the amp section.  it's been said by more than a few that it almost sounds like the THX00 was tuned for the m9XX, and it's hard to disagree.  But I also think that almost any low impedance cans with powerful magnets in the drivers (the THX00 is over 1 Tesla) benefit from the current the m9XX pushes.  The m9XX doesn't change the THX00's signature, it just tightens everything, smooths some of the rough edges out and adds a level of detail and transparency.  Essentially it enhances the THX00's strengths (bass power, fun factor) while polishing its perceived weaknesses (detail, bass texture, imaging).  What you're left with is a heck of a fun, yet technically proficient pairing.
I also spent about an hour with the TH900 with this pair and the bass on the TH900 with the m9XX was legendary: controlled, powerful, deep, no bleed over.  Everything I said about the THX00 applies here, except with the TH900's even more powerful bass.  If you don't like the TH900's hard V signature, this won't "mellow" it out all.  Again, what the Grace does is get out of the way and lets the headphone do its thing.  If you're a fan of the TH900, you'll love this pairing.  If you aren't a fan of the TH900 sound, you're still going to dislike it.
 With the Sennheiser HD650 the pairing is incredibly smooth, detailed and refined with gorgeously textured bass and smooth, if a bit veiled, treble
There are two approaches to properly amping the HD650: 1) something that shows the headphone's inherent character or 2) something that provides a little more treble energy to shake off the "sennheiser veil."  If you want the latter, this isn't the pairing for you, because as previously stated what the Grace does more than anything is get out of the way and lets the headphone do its thing.  That means this pairing does much more of the former, you hear how the HD650 really sounds.  It's incredibly detailed, the bass has a sort of refined grace, the treble has a relaxed smoothness that's simultaneously detailed.  To some this sounds veiled and boring, to others it's the pinnacle of engaging treble and a deep soundstage that sounds like you're watching a concert from about the level of the soundboard, as opposed to the front row.  If you want to "shake off the veil" I'd go with something a bit more energetic, like maybe a Lyr (with either solid state or more energetic tubes).  
This pairing really shows what the DAC section is all about though, as the microdetail somehow manages to be both precise and crisp yet musical and relaxed.  It's a sort of elegant beauty that sounds really classy.  It's probably not the amp I'd use if I was building an HD650 system from scratch, but I've come to realize that has more to do with some dissatisfaction I personally have with the HD650's relaxed signature.  I wanted an amp that would "fix" it, and as I've already stated, the m9XX isn't going to fix any issues you have with a headphone's signature, it's simply going to reflect the base signature, and refine the more technical aspects.  I think of it like a photographer making a model look as beautiful as possible with skill in photography, without using photoshop to "fix" things.  It brings out the best of what is available.  
Grados are frighteningly fast and energetic, gain a bit tighter punch in the midbass, and become an even more fun, if still a strictly technically flawed listen
I think there tend to normally be two camps with regards to the Grado sound: those that think it's complete trash that hipsters love and those that can't accept that there might be ANY flaws whatsoever.  I tend to fall into a middle ground.  The SR60e is one of the first three headphones I bought when I got into headphone audio (the Denon D1001 and Audio Technica AD700 being the others) and I'll always be fond of the sound.  They can bring a lot of energy, especially to older classic rock recordings.  They provide a lot of speed on the cheap.  But I also realize that they're honestly technically deficient if the goal is to reproduce what is in a recording.  Again, the Grace won't give them some semblance of sub bass, it's still as rolled off as ever.  The Grace will, however, "perk up" the Grado upper midbass hump, providing classic rock kick drums a bit more thump, thus somewhat equalizing the perception of the signature, without changing the Grado house sound.  Grados are notoriously current hungry, and the m9XX defnitely provides the current they crave.  This results in a lot more refined sound.  I tried the pairing with the SR80e and the SR225e.  The Grace really took the SR225e to a great place.  The DAC section really enhanced the soundstage and imaging.  The amp section gave their already good speed the high octane it needed to become a gloriously fast headphone for metal and prog rock.  The amp section also gave that bass hump some authority and depth that it normally lacks.  The SR80e didn't see quite the same benefit, though you got some semblance of a soundstage (unusual for the SR80e, which to my ears has virtually no depth or soundstage width).  The SR80e's at times flabby midbass tightened up.  The fatiguing upper midrange smoothed out just a touch.  It's not going to turn a SR series Grado into a GS1000, but it will take the Grado house sound to the next level, while staying unmistakably Grado, for good and/or ill.  
Other miscellaneous pairings I tried
Just going to dump my pairing notes with headphones that are either less common or that I didn't spend a TON of time listening to:
1) TheAudio Technica  ESW9A is probably my most difficult headphone to amp, in the sense that most amps tend to actually make it sound worse.  As a headphone it's kind of muddy, has boomy bass, and isn't particularly transparent.  Treble/upper midrange is kind of weird and veiled, but with a little sparkle on the very top.  The pairing essentially brought all these qualities to the fore.  It did add a bit more detail, but overall, yeah, this headphone still sounds better out of an iPhone than it does when amped.  It's pretty though, and very portable.  A good headphone to non-critically walk the dog, not to plug into an amp and listen to carefully
2) The Shure SRH840 is probably the easiest headphone I have to amp.  It's so workmanlike that it just does its job with almost anything.  The pairing worked well.  The Grace, as per usual, added a bit more detail retrieval and transparency and firmed up the bass.  If you want a slightly warm, soft U-shaped monitoring style headphone with good treble clarity, this is it.  I love this headphone, but it won't wow you immediately.  This pairing is an ultimate all-arounder when it comes to closed headphones.  It does everything very, very well, but doesn't amaze you with any single aspect.  
3) The Audio Technica M50X has issues with bass bloat at times, and the m9XX helped with that.  The m9XX couldn't do much about the lack of soundstage though, it still sounds like you're having sound pumped into the middle of the brain, and imaging is still basically only left middle and right, no nuance.  The m9XX did refine the treble a bit though.  the M50X is a headphone that is notorious for sounding the same pretty much no matter what is amping it, and that held true here as well.  
4) The Audio Technica AD700 has some issues with grain, and the m9XX brought that out.  However, the AD700 is also incredibly detailed and spacious and the m9XX highlighted and enhanced that.  At times the soundstage was almost so vast that imaging lost a bit of coherence.  Crossfade helped with that, making for a large (thought not cavernous) soundstage that was very precise imaging wise.  The AD700 is one of the most rolled off headphones in sub bass I've ever heard, and that stayed true with the m9XX.  
5) The Koss KSC75 is an ultra portable on ear clip on headphone.  But its quality is incredible for $15.  THere are a lot of $100 headphones it wipes the floor with.  I would never use it on the m9XX on a regular basis, I strictly use it as a portable "walk around outside" headphone.  But here goes anyway: The KSC75 has great treble detail and sparkle, though is fairly rolled off in the bass (mostly due to the way it just sorta hangs around your ear).  The m9XX made it sound even more spacious and detailed.  
6) The Denon D1001 is essentially the same headphone as the long running and budget popular Creative Aurvana Live.  I believe Fostex actually makes it.  It has a budget version of the Fostex house sound regardless.  It has pretty great midbass and sparkly treble.  It's certainly a V-Shaped headphone, which helps hide its weaknesses (a bit congested and not super resolving).  I was actually surprised how much the m9XX improved this headphone.  The sometimes boomy bass was tightened substantially, and gained more extension.  The muddiness was cut fairly dramatically.  I could hear some grain, that the muddiness had never even allowed me to hear before.  Grain is always preferable to muddiness, so this was a welcome revelation.  This is another "knock around" headphone.  I've owned it and enjoyed it for about 10 years now and it was nice to have some new life breathed into it.  It's still not an amazing headphone, but the Creative Aurvana Live version is still a bargain (Denon long ago discontinued this, at the same time it notoriously switched from Fostex for the rest of the DX000 serious, leading me to believe this is a Fostex headphone).  But I mean I don't know anybody who would buy an amp like the m9XX for it.  
Notes on the filters:
The filters are very subtle, so it took quite a while for me to suss out their effects.  They don't so much change the frequency response much, their primary effect is in how they handle the delicate balance of rich, absolute timbral accuracy and maximum clarity.  I don't think people realize that this is often a tradeoff, as super compressed music with lots of treble can often cause aliasing distortion with ultra-high-quality DACs.  I think this is a lot of the phenomenon people notice when they say certain top-shelf DACs are "very harsh to bad sources."  Sometimes it's almost like people here relish a DAC that makes pop music sound like crap, as if that's a badge of pride.  Grace, however, decided to give you the option for a more detailed DAC and a more forgiving DAC (to simplify things greatly).
F1: This is given the default spot as the filter, and I think for good reason.  It's the setting that will probably sound best, for most people and how they use the m9XX and the music they'll most use for it.  This is the best setting to use if the Grace is both your DAC and your amp and you're listening to compressed music.  There are two aspects to this setting (like all the settings): fast roll-off and in phase modulation.  The first essentially cuts down on aliasing distortion issues that can happen in highly compressed music with lots of high frequency content.  The second keeps a linear phase response, for maximum preservation of the source signal.  The latter can be bad if you're using an amp that isn't the Grace, ie using the RCA outputs to feed an amp or powered speakers.  Something about how they built the amp section of the Grace seems to do away with the intermodulation issues that can happen with a linear phase.  This intermodulation effect seems to be especially problematic with tubes, which can have microphonic tendencies.  I honestly couldn't tell much difference between F1 and F3, until I put the m9XX in front of my SSHM hybrid tube amp, and there the F3 setting sounded much cleaner than F1.  
TL:DR: if you're listening to typical pop/rock music that is loud with a lot of treble, and you're not using an amp after the Grace, this is probably your best setting.  
F2: This is probably the most accurate filter, and what would probably measure the best in objective testing.  It is susceptible to aliasing issues with highly compressed, treble music.  ie pop music will sound somewhat harsher with it.  It can also theoretically have intermodulation issues if it's being used with an external amp.  But when using it with well-recorded, non treble-heavy material, and the Grace as an amp, it provides the ultimate in transparency.  
TL;DR: if you're listening to well recorded and mastered music and not using an external amp, this is your no-compromise absolute transparency setting.
F3: This setting is the ultimate "fix problems" setting, everything will sound good out of this setting, regardless of what is going through it, and you'll never have to worry about problems.  It sacrifices a bit of complete transparency to cut down as much as possible on aliasing distortion and intermodulation distortion.  
TL;DR: use this if you're listening to highly compressed music with very loud treble and using an external amp out of it (especially at tube amp), or if you're experiencing distortion issues and you're not sure what part of the chain they may be coming from.  
F4: This is probably the filter that can, theoretically, get the absolute best sound out of the m9XX's DAC section.  It produces the full, rich tone, without giving worry to aliasing issues in high treble energy music, but shifts the ringing to reduce any intermodulation effects that might happen with an external amp (especially a tube amp)
TL;DR: use this if you primarily listen to exceptionally well recorded music and are using an amp (especially tubes) after the m9XX.
This is an INCREDIBLE piece of gear.  It's so versatile that it's astounding.  I'm not an IEM guy (can't stand the feeling of having something in my ear canal) but it can effortlessly amp those with complete silence, and it can drive an HD650 very well.  Heck, several people even say it's a great pairing with the Sennheiser HD800.  It's so well designed from all angles: look, feel, build quality, feature set, sound quality and just some indescribable "ahhhhhh" feeling of satisfaction every time I look at it.  Where it really shines are the current hungry high end but low impedance headphones that have really been a growing market segment these days.  The crop of easier to drive planars and low impedance dynamics will sound better than many thought possible through the m9XX.  It's not going to blow you away on a first listen though.  It's not going to grow a subwoofer in your bass deficient headphone, pr give a non-detailed headphone HD800 level resolution.  But it will take the headphone that it's being given and shine it as well as it possibly can.  It's not going to power a HE-6, but it can handle almost every "normal" headphone with aplomb.  I'm pretty sure this is the last DAC or amp I will ever own, unless there's some crazy leap forward in technology.  
I think of it this way: If this thing was just a DAC, and had no features (no crossfeed, no filters, no volume control, etc) it would be a bargain at $399.  If you had a unit that added the features it has (crossfeed, filters) for just that add on unit, you could charge $100.  If it was just a solid state amp, given its ultra low impedance, the way the volume control and high power mode work, the cleanliness, just the amp section would be a bargain at $250.  Put that all together and you have a product, that on pure sound quality alone would be a bargain at $750.  Then when you combine the convenience, elegance, and quality of the build and form factor, this is easily a $800-$1000 product.  It would make a lot of "best value" lists if it cost $899.  Grace and Massdrop got it to us for $499, which makes it a stupefying value.  
You can throw this in a messenger bag, without any worry, and you can have sound quality that will put many $2000 systems to shame.  You can power everything from an IEM to a HE500 and never feel that your gear is being compromised.  It's an all around solution that somehow manages to make no real compromises at a budget friendly price.  If your headphones don't require s small scale nuclear power reactor to drive, I have one piece of advice about this:
If you have the chance BUY THIS THING
Great review.  Really liked your descriptions of the filters.  Thanks!
Great Review! Now I'm actually considering this piece of equipment.
Eh are you sure they can't drive the HE6's well?
Like, I've heard they make the K7xx's scale amazingly, and are a perfect match for the HE400i, but there are also claims that it can drive the LCD4's with no shortcomings, and the HD800's.
If they can't drive the HE6's should I just avoid them? (I own a pair and my Valhalla kind of got knocked off my counter by my dog)


500+ Head-Fier
Pros: Detail, Versatility, Overall SQ, Features, Size, Portability option, Small wall adapter, DSD support, Fantastic with planar magnetic cans.
Cons: Stacking limited to under the device, Doesn't pair well with some headphones, No RCA Inputs, No carrying bag/case.
The m9XX is a small desktop DAC/amp that doubles as a portable one. Obviously, it will have more power when it’s plugged into the wall, but it packs some power driven just from a USB connection as well, and should work well in that mode with almost all IEM’s.
Grace Design are known for their top of the line audio products, almost all of which are targeted towards the very high-end audiophile community. Massdrop, a company that features products at lower prices (done through group buys), worked with Grace Design until they came up with a DAC/amp that was very serious about audio and reasonably affordable to the public, or at least a lot more so than the previously premium products offered.
Sound-wise, the new m9XX is designed after the flagship m920, and is supposed to be on the same level as the m920 in audiophile applications. So what’s different, and why the price drop? The m9XX leaves out many of the inputs that the m920 only needed for pro audio recording and such. Take them out, and with new technology (leaving out the Sabre DAC chip and implementing instead the top-of-the-line AKM AK4490 chip, which performs much better without the need for all the expensive components), together with the guarantee of a group buy, and a $500 DAC/amp based off a $1500 one suddenly becomes a reality.
You might (or might not) be panicking a bit about the implementation of a different DAC chip than the Sabre. However, you should know that the new Schiit Bifrost, a very well regarded $400 standalone DAC features this same exact chip, and received excellent reviews. This AKM chip is now being implemented in many products across different companies, as it doesn’t require other expensive parts to make it sound as good as the Sabre, while also supporting many options, such as 256x oversampling, 32-bit processing, and sample rate compatibility from 44.1kHz to DSD128.
So don’t even think of thinking that this chip is a “cheap alternative”, because it’s not. It’s a very solid sidegrade, and even an upgrade in many ways. Since the m920 used the Sabre chip, it required many other needlessly expensive components, which they were able to work around for the new m9XX, due to the versatility of the AK4490 chip.
“So then, how do we know that Massdrop is good at making products? Weren’t they only selling other people’s stuff until now?”
Hey, good question. In terms of collaborations, they haven’t had too many. But they did make one product before – the AKG K7XX, now known as the greatest $200 headphone one can buy. Massdrop’s first collaboration, the K7XX (made alongside AKG), has received reviews unlike any other headphone since the HD600 was released 15 years ago. I’m serious, the K7XX was a massive success (to say the least), and was the only open headphone anywhere near its price range that came dangerously close to throwing headphones in the mid/high tier category under the bus. Nothing else even came close to the sound quality it provided at the time (about a year ago) for its price, and even now, there are few options that can match its price/performance ratio.
In the first week, just through Massdrop’s website, it sold ~2782 pairs (if my memory serves correctly), and every time they offered it again, they’ve gotten thousands of happy buyers, until it came to the point that Massdrop had to limit the amount of K7XX’s sold for fear of a lack of materials. It should be on Massdrop every 2-3 months or so, so if you haven’t gotten a pair yet and are looking for a great budget king, I highly recommend it!
So the point of all this is that Massdrop is not only reliable when it comes to mass production, they also know how to engineer great products that seems to elude the grasp of many companies. Since Massdrop is very active with the customers (answering questions on the forums, among other things), they have a greater sense of what’s needed, what is not, and what has to be improved in the future. And just like in “Back to the Future”, 2015 is, in this sense, the future. Massdrop has been around for a while, and accumulated a lot of knowledge during the interim that helps them avoid mistakes that plague other companies. They know what works – as is evident by the massively popular K7XX.
So it’s no wonder that people were excited for their new collaboration, the m9XX. Due to the nature of Massdrop, people are expecting this to punch much above its price, and because of that I will view in it that light as well.
I'd like to thank Massdrop/Grace for the m9XX sample - it's a really great device, and I thoroughly enjoyed writing this review. I am not affiliated with Massdrop in any way though, and there was no financial incentive for writing this review.
I'd also like to thank Audio46 for giving me the opportunity to demo many of their headphones for this review - without them, the review would not nearly be as comprehensive as it turned out to be.
I’m a college student. Not some retired tenure professor living off nice earnings. Because of this, my goal was never to get “the absolute best performance” but rather “get the best performance/price ratio”, due to the fact that I don’t have a job (duh, I’m in college). My yearly spending money is a few hundred dollars, which is more than some, but does make it hard to get good gear in a pretty expensive hobby like this one.
The point? Until now, almost all my reviews were for “budget kings”, like the K7XX, HE400S, Shozy Alien, Aune X1S, and others. Reviewing an item that is the mid-tier category, and isn’t for budget people like me, is a new development, and I’m not going so easy on this one as I was able to do by others, since it has an automatic decrease in performance/price as a mid-tier product.
So all of you students, and people who actually have a budget, I hear your plight, and my conclusion will have something specific for you guys too, not only for the people looking for the best of the best, regardless of cost.
And for all you audiophiles out there, I trust my ears more than my eyes – I’ve blind tested between headphones and sources more times than I can count (more for fun and competitive purposes that for testing, I must admit), and you better bet I can tell the differences between flagships easily by now. So with that said, I hope both parties won’t doubt (too much, anyway) my credibility as a music lover and aspiring audiophile, yet as a down to earth and practical guy.
To help you decide if you should buy the m9XX. That’s it, nothing more, nothing less. To that extent, many of you are probably wondering how it compares to the ODAC/Objective2 stack, Schiit Magni/Modi, DACport Slim, and Aune X1S. Although I won’t be able to do direct A/B comparisons, I think I’ll be able to answer at least some of those questions with confidence. That will be later on in the sound category, in the part where I compare different DAC/amps I own.
As for headphone pairings, I should be able to include analyses of many headphones, such as headphones from AKG, Beyerdynamic, Sennheiser, HiFiMAN, Grado, etc. So if you would like to know if your headphone pairs well with the m9XX, odds are it will be talked about in the sound section below.
Packaging (Pictures):
Build Quality, Design, and Features:
The build is solid, there’s not much to talk about here. The metal seems to be about half an inch thick, which not only makes it more solid than the competition, but reduces heat as well. It has a solid feel to it, and while it is a bit on the heftier side, it’s actually quite light for the amount of metal in this device. The volume knob is also nicely built, and is of a lighter metal than the case. Despite doubling as a button (and being made to turn 360 degrees), it doesn’t feel loose in any way. The power supply is really small for the amount of power it gives, and is a much better form factor than, say, the Aune X1S’s monstrous power brick. The two USB cables included feel nicely built, no problems here. If you’re looking for audiophile Moon-audio cables you’ll have to bring your own, since the m9XX uses Monoprice cables (as it says of the packaging). These are the higher end models though, and I’ve always been happy with their cables to begin with, so this shouldn’t be a problem for anybody.
The case is made of brushed metal, which never feels cold to the fingers (as other DAC/amps I’ve seen do). Instead of being a black box, like the ODAC, the top is rounded off on both sides, with the Grace logo and “m9XX” printed on the front rounded side, and the Massdrop logo on the back. The silver volume knob is on top, and sort of reminds me of the JDS Element, although in pure looks it’s a little behind the Element (barring the display, extra inputs, and features the m9XX has that the Element doesn’t). Overall, it may not look as impressive as Grace’s $2000 offerings, but it’s definitely a nice looking product, much more than the pictures convey.
As for features, this product comes stacked with them. I’ll do a quick rundown of the features that may not be so obvious, since all the other information can be found in the online m9XX manual, and is much better explained there than I can do here. Let’s go through the features other DAC/amps in this price range may not have:
- Two headphone output jacks, so you can effectively compare headphones, and let someone else listen without having to give it up yourself. This may not seem like much, but it’s been a while since I could let a friend listen to my music or watch a movie in a hi-fi setup, because there’s only enough room for one darn headphone. I’ve had amps with two headphone jacks, and it was useful more times than I can count. It’s important to note the current is shared between the two jacks, and that the right one mutes the RCA line outs from the back, which I’ll talk about now.
- The RCA outputs in the back allow a line-out signal, bypassing the m9XX’s internal amplifier and allowing you to hook it up to your own. Like I said, the right headphone jack mutes the RCA outputs. This isn’t a mistake – it was implemented to allow you to toggle between speakers and headphones, which is very useful for sound testing. If you want to use both the line-out and headphone jack at the same time, just use the left jack.
- Implementation of the processor to prevent “over current”: since the m9XX’s output impedance is extremely low (only measuring at 0.08 ohms), there is inevitably a higher chance when plugging in the headphones of a high current flow. Not to worry though – the internal processor, when sensing this, will temporarily shut down the internal audio supplies, thus circumventing the problem. I haven’t seen any other DAC/amps deal with this problem, which kind of worries me. To be clear, I haven’t gotten an over-current yet, even when plugging in my headphones. So it’s safe to assume that getting an over current signal (“OC” on the display) is infrequent and not likely to happen. Still, I’m glad that Grace/Massdrop went out of their way to make sure this is never a problem.
- 2 modes: USB-only, and a wall adapter option. You can choose to draw power only from the USB port, which drives almost all IEM’s, and even some low-impedance full-sized headphones as well. There’s also a high-powered option, with a power supply that plugs into the wall. That mode will should drive any and all headphones with authority.
- Plug and Play: the m9XX can be used driverless up to 24 bit/96khz. For rates above that (and DSD), the m9XX has a Windows driver. MAC users can be driverless all the way up to DSD. So if you want to listen to the m9XX in the office, library, or some other place where it’s not authorized to install software on the computers, you can do so with very little compromise – most people can’t hear between 96khz and 192khz, or if they can, it is a minimal difference. To the ones who do – hey, it can still play DSD, just install the driver first.
- Volume Knob: Yeah, all DAC/amps have this, I know. But this one increments the volume in exactly 0.5 decibels per step, so no channel imbalance or imprecise (or exponential) volume headaches here. The knob has a slight, but satisfactory “click” to it that instantly lets you know how many volume steps you just incremented. To be clear, it doesn’t actually click audibly, but there is some resistance between each step than achieves the same purpose. The knob also doubles as a button – press once to mute the audio, and hold down for 3 seconds to access the menu.
- Display: the m9XX actually features a nicely lit display, which allows you to see what volume you are at, as well as access the menu and toggle options such as crossfeed (useful for older recordings), USB input and Toslink input, Display Dimmer Mode (turns off 7 segment display after 5 seconds of inactivity), 4 DAC filters, driverless vs. driver enabled mode, and sample rate display.
I won’t go into the details of each one, as I said before, but you can find all the information in the manual – which I highly recommend you read – I usually skip the manual as a consumer, but the m9XX’s manual is a must-read for anyone that actually wants to know how to use the product. Here you go:
DAC Filters:
This option is rarely included in this price range, with the exception of the Aune X1S, which I couldn’t hear the difference between filters anyway. I hear some differences between the 4 filters on the m9XX, but I’ll have to experiment with them a bit more before I come to any conclusions. Stay tuned!
Update: I haven't been able to find any clear differences between the filters to my ear, and I'm not sure if any differences I hear are real, or only in my head, so I will refrain from discussing them here.
It’s very hard to describe in words the sound differences between DAC/amps, or the impact it has on a certain headphone – this is why there haven’t been too many critical sound impressions so far. The m9XX, as others have said, sounds very detailed (much more so than the “budget” offerings), yet also sounds musical, and not analytically dry. What do I mean by that? Well, it seems like with most headphones, the m9XX releases the full potential of the cans, as opposed to keeping it on the “safe” side. That’s how (you’ll see soon) the HE400i sounds very musical, and the m9XX almost goes out on a limb to deliver its full planar magnetic bass. It’s easy to get lost in the music with the m9XX, but not in a way that puts you to sleep – rather it lets you truly enjoy the music, while also giving tons of detail and accuracy. I find myself often technically enjoying the performance of a DAC/amp, but not really enjoying the music, and certainly can’t immerse myself in it. With the m9XX, I could do both.
The m9XX is very transparent, allowing the innate quality of the headphone to shine, rather than “fix” it with coloring like some others do. Headphones that scale well with equipment (such as the K7XX) should scale well with the m9XX, and might even become a completely “different” headphone. Paired with the K7XX, for example, it’s hard to understand how the K7XX costs only $200, when with the m9XX it’s technically capable of a lot more – things I never even heard in the K7XX until now.
So to quench the thirst for critical impressions and less-vague sound descriptions, I’ve compiled my conclusions on some pairings with the m9XX, as well as some impressions I’ve had during certain songs. Please note that I wrote more notes on less expensive pairings, as those had plenty pros and cons regarding the matchups. Moving on to more expensive headphones, it’s harder to take notes (since they are already technically very good on their own), but easier to hear the overall trend in tonality, and easier to comment on the pairing in general. These weren’t the only listening tests I took, but the ones I actually bothered to type down here. The conclusion was made after all my listening tests, not only the ones done here.
I'd like to give a huge thank you to Audio46 (also known as H & B Digital) for allowing me to demo the headphones needed to write this review. Due to their generosity, I was able to make this review as comprehensive as I could, and without them, it wouldn't even have half the information that it does now. They're by far the best headphone store I've been to in NYC, and I'll definitely be buying from them if the need arises.
(OC Remix) Seven Songs for Seventh Saga: II. Water
(OC Remix) Apex 2014: A New Challenger:  A New Challenger!!
(OC Remix) Dues Ex: Sonic Augmentation:
The Search for Ambrosia (NYC Streets)
Human Soldier (UNATCO)
Siren Synapse
Adele (21):  Set Fire to the Rain
Alva Noto & Ryuichi Sakamoto – Vrioon: Uoon I
Animals as Leaders – The Joy of Motion:
The Woven Web
Para Mexer
Steely Dan – Aja: Aja
Kronos Quartet - Pieces of Africa: Mai Nozipo ('Mother Nozipo') - Dumisani Maraire
Fleetwood Mac – Rumours: Second Hand News
Dvorák - Symphony No. 9 - Karel Ancerl, Czech Philharmonic:
Diana Krall – The Very Best of: Peel me a Grape
Shpongle: Museum of Consciousness: Juggling Molecules
Sweet Georgia Brown (Chesky Recordings)
Gorrilaz: Plastic Beach
Chrono Cross: Scars of Time
DUNU DN-2000J (on low power mode):
This is a fantastic pairing – if you’re getting the m9XX for your open-back headphones or CIEM’s, and have the DN-2000J in your collection, you’re in for a treat. The DN-2000J now sounds extremely musical, and the amount of detail in both the m9XX and DN-2000J complement each other extremely well without sounding dry or analytical. There’s a fantastic bass here that extends very low. Not anywhere near over the top, but still very welcome. Highly recommended pairing.
Woven Web – Everything here is crispy clear, and sounds very natural. No overbloated bass, and sounds very musical, something which I haven’t heard on the DN-2000J. Soundstage is very good too, and is really hard to tell this is actually an IEM. Detail could be a bit better, but that’s coming from an ideal perspective – detail is definitely above average here.
Aja – Vocals sound really great, not too forward but nicely placed (unlike other headphones, which sometimes sounded distant with this song). Background sounds are nicely detailed, and imaging is spot on. The whole song sounds very natural, and not artificial in any way.
Second Hand News – I wanted to see how this pairing fared with this song, especially since some headphones sounded thin here. I’m glad to say that it doesn’t sound thin in any way; to me, it actually has a nice hint of warmth, which doesn’t destroy the clarity in any way.
Sweet Georgia Brown – There’s a lot going on in this song, and the DN-2000J handles it very, very well. The drums and cymbals sound perfect, as does the piano. Everything is nicely spaced, so it really gives the impression of a 3D-like recording.
Juggling Molecules – This pairing makes the song sound very musical without being closed-in in any way. The bass is nice quantity-wise, and I really get into the mood with this song. Again, there’s a hint of warmth which is very welcome, and much appreciated.
Sennheiser HD 650:
(Note: These were taken straight out of the box, no burn-in at all.) The HD 650’s bass would work better with the X1S, in my opinion. This is unfortunately a problem with the HD 650, not the m9XX. To me, there’s some things about the HD 650 that needs to be “tweaked” to sound good with rock, electronic, and even vocals. That’s enough for me to say I don’t like this pairing.
Search for Ambrosia – I’ve heard better, although that’s probably more due to the HD 650 than the m9XX. The drums don’t have that “punch” I really like, and overall there seems to be a veil that muddies up the music, although it’s easy to forget about after a while. Imaging is good, and allows me to hear more of the details, especially at 1:56. The DAC/amp is doing an impressive job at bring a high resolution to the table. At 2:23 I hear the helicopter sound better than I have with other dac/amps.
The Human Soldier – the nature of this song makes the highs a bit forward, although left/right differentiation is definitely better than other DAC/amps I’ve heard. The extra details are also easily heard in this track, a leagues ahead of the budget stuff – clarity is also much better, and there is no veil in the highs. Not much instrument separation at 1:15, and at 1:45 it’s very easy to hear the “tick tick” in the background. Nice punch at 2:29, even though it doesn’t extend deep I don’t think it’s supposed to.
Siren Synapse - Very nice bass punch at 0:21, this has many ways to go wrong, and it doesn’t. At 0:38 there’s a wonderful bass response, well rounded and articulate. Same goes for 2:23. Bass in this song is sublime.
The Woven Web – 0:15 guitar is a little too bloated for my tastes, although that’s definitely due to the 650’s extra bass, not the m9XX. 1:29 seems a little slow, although it’s interesting that at 1:45 the (slightly overbloated bass) doesn’t overpower the rest of the spectrum.
Para Mexer – this is a little better, although the HD650 still has too much bass and a veil for this song to really shine. Bloat’s there, albeit at a lesser level. 1:08 the “hissing” is clearly audible (don’t worry, that’s part of the song), and apart from the rest of the spectrum.
Adele: Set Fire to the Rain – the piano is tamer than I would like, her vocals are a little lacking in resolution, and a little “compressed” or veiled, as it were.
Apex 2014: New Challenger – bass here is good for once, extends low and is articulate (not over the top quantity wise though), but I don’t only listen to this song, and on other tracks bass is a hit or miss.
Uoon I – this sounds good for once, and the imaging is on point. Piano sounds great here, and the song is really enjoyable. Detail is high throughout the song.
The HE400S sounds a lot like the HD650, so it makes sense that they would have the same results with the m9XX. Although it sounds good, certain things like the bass and vocals sound held back and “veiled”. Even though the HE400S are planar magnetic, like Head-fi reviewer Money4me247 said, these are tuned like a dynamic headphone for the low end, so other planar magnetics will work much better than the HE400S in this regard. The HE400S (and HD 650) don’t really scale nearly as well as the K7XX does; if I had two compare the two using only the m9XX, I would say the K7XX is the better headphone by far.
Para Mexer – This song is very detailed, but the guitars seem a little unnatural, and a little to upfront for me to tell anything else.
Set Fire to the Rain – Vocals seem a little suppressed, which surprises me knowing how good the HE400S can sound with vocals. Details are excellent, I can hear the background sounds very well.
Peel me a Grape – Vocals here are still not the best I’ve heard, although the detail is great again.
Second Hand News – Vocals are muddy here, confirms my suspicion that this pairing isn’t great for vocals.
Aja – There’s a nice sense of imaging here – you can tell where everything is coming from, and gives you a very 3D-like sound.
A New Challenger – Bass extends really deep here, and shows the planar magnetic quality of these.
Juggling Molecules – Detail is really great here, and imaging is spot on too. Gives this song the attention it deserves, in my opinion.
The Woven Web – A little too much bass here in the guitars, seems bloated like the HD 650. It’s different from the HD 650 in respect to 1:29, where the HE400S holds up quite well and doesn’t seem clustered, while the HD 650 is just all over the place with that part of the song.
HiFiMAN HE-400i:
The HE-400i is fantastic paired with the m9XX, and I highly recommend the pairing. The planar magnetic bass quality is definitely present in full force here, and I’m just in love with everything this pairing has to offer. The only downside I can imagine is that the highs can a bit tame at times. Other than that, there’s nothing I could fault it with.
A New Challenger – The bass here digs DEEP – definitely see the planar magnetic bass in these. It’s rich, articulate, and clear, nothing like the HD 650. Highs are a *tad* tamed, but still noticeable and listenable.
Seven Songs for Seventh Saga: II. Water – Cello is nice hear, although I’ve heard it more naturally represented (this is because of the HE-400i’s sound signature). Bass response is spot on again, really digging the bass on these. Highs aren’t too tamed here. Separation is good between the different cellos.
Gorrillaz: Plastic Beach – instantly can hear the clarity of the air, and the wide soundstage. Separation is good, especially given there’s a lot going on this track.
Mai Nozipo – the extra bass is perhaps a bit unnatural sounding here, but otherwise the drums are sublime. This track is VERY detailed with this pairing.
Uoon 1 – The highs are more present during this song, and more “in your face.” The low response extends really down low throughout the whole song, which can be missed with other headphones due to its very subtle low-end sound. The high “noise” is very detailed here.
Second Hand News – loss in clarity from the beginning, and I know that’s not from the recording. Other pairings of the m9XX has this song singing, this one doesn’t. It seems to be due to the headphone, though I can’t imagine why. Vocals could be better here.
The Woven Web- very good pairing. The Guitars here are top notch. 1:29 is fast and accurate, and clean. Good bass, but extremely clean and no sign of overpowering, like the HD 650.
Symphony No. 9 – the HE400i’s extra bass doesn’t hurt it too much here, although I wouldn’t use this headphone for orchestral recordings in the first place – it doesn’t seem to fit its sound signature.
Set Fire to the Rain – everything here is sublime; the piano, the bass response (which I previously missed before with the HD 650) is clean and planar magnetic here. Vocals are jaw-dropping, I could literally listen to this all day with this pairing.
The m9XX and the K7XX make for a really great pair – the m9XX loads every song with detail, and with the K7XX’s large soundstage it’s a scary combo. If it seems like overkill to get a $500 DAC/amp for a $200 headphone, know that I thought the same thing before listening to this pairing. The K7XX scales very well with the m9XX, and you’d be hard pressed to tell this is a $200, or even $400 headphone.
Peel me a Grape – Vocals are much better here than other sources I’ve listened to. Cello doesn’t go very low though, not like the HE400i does. Detail is spot on here, and much, much better than the budget DAC/amps I’ve used.
Second Hand News – Left/right differentiation is really great here, and separation is excellent too. Soundstage is wide enough for me to know I’m listening to the K7XX here, so I’m glad about that.
A New Challenger – Soundstage is wide here yet again, but the bass doesn’t go as low as I’d like it too. This I think is more a problem with the K7XX than anything.
Uoon I – Very detailed, I’d think I was listening to a higher tier headphone just from the detail alone. Bass extends nice and low here, very happy about that.
The Woven Web – Guitars have a nice helping from the bass, and overall the song sounds clean, not like the HD650. Detail is great enough for me to hear the cymbals (which is very much in the background) well. 1:29 isn’t clustered by any means, and the song on a whole seems to flow rather well.
Seven Songs for Seventh Saga: II. Water – The cellos here are very detailed, and are very musical.
Mai Nozipo – The drums here are nice, but with a bit too much help from the bass. Violins here seem technical, and not musical.
Para Mexer – This song really shines, the guitars are just fantastic. I can hear background sound I know I wasn’t able to hear with the X1S, or any of the other budget DAC/amps I’ve tried. I know this is getting a bit repetitive, but the detail here is again, spot on, and nowhere near what the X1S/ODAC/O2 can provide.
Audio Technica ATH-R70x:
This pairing isn’t one that will wow you on first sight, but definitely benefits from the m9XX’s detail, and opens up the bass in the ATH-R70x. I would recommend it over pairings with budget dac/amps (i.e. ODAC/O2, DACport Slim, Aune X1S) – the even-handedness of the pairing and the detail brought to the table really opens the R70X up. If you want a pairing that is the jack of all trades, this one should do it, and everything well.
Aja – Bass response is good, clean without having a lot of quantity. Imaging is very decent, soundstage is not overly large, but has a nice amount of space. Separation is good here too.
Plastic Beach – better on the HE-400i, but still loaded with detail. It’s as good as it’s going to get with this specific headphone.
Mai Nozipo – Drums here are spot on, and incredibly detailed because of the m9XX. Violins are nice, and don’t seem tamed here. The different types of drums here are easily differentiable, and are all a massive treat for my ears.
Uoon 1 – Bass doesn’t disappoint here and extends very well; that’s really all I was testing this track for with the R70x. Piano is okay here, and separation is nice.
Chrono Cross: Scars of Time – This song is one of my favorites despite being a soundtrack, and the guitar here is nicely detailed without being too over the top. Bass extends well here as well, especially in the second half of the song. The song on a whole sounds fantastic with this pairing.
Juggling Molecules – Soundstage here isn’t huge, but is well rounded and well defined. Seems a little tame, but speed is spot on – more so than other pairings.
The Woven Web – guitar is good here, and nice separation compared to other DAC/amps. A little more clustered though than with the HE-400i.
Set Fire to the Rain – nice vocals, although it seems a bit held back, and also seems very neutral. Separation is good here, and soundstage is nice and wide as well.
Grado RS1e:
These two are excellent for any classical or jazz lover, who doesn’t mind semi-bright highs. Not too much bass here, but this headphone isn’t meant for that. If you have audiophile recordings, this pairing will serve you well.
Set Fire to the Rain – Vocals are crispy clear, can almost be too much brightness for those not used to the Grado sound. No sibilance though.
The Woven Web – Guitars are crisp here, no bloating of the bass. 1:29 is fast, the m9XX/RS1e doesn’t lose any speed or get caught up in a tangle, at this pairing handles the song with aplomb.
Seven Songs for Seventh Saga: II. Water – Cello here could be a bit more detailed, but still a very enjoyable experience. Smooth sound throughout the song.
Chrono Cross: Scars of Time – Flute isn’t overly bright, a relief. Guitar is nicely done, and I can every detail of it. Good song for this pairing. Second half of the song is displaying so much detail I’m FEELING the emotion of it.
Para Mexer – Very, very good separation and imaging, and this pairing doesn’t fall being in any way. I’m hearing new things in this song I wouldn’t have thought I could get at this price.
Uoon 1 – Pianos could be more detailed, although detail of the “noise” is again, spot on. Bass is good here, the pairing doesn’t omit any of it.
A New Challenger – bass doesn’t seem to go really down low, although that’s the headphone, not the m9XX.
Peel me a Grape – A wonderful pairing, everything is how it’s supposed to be. The background cello is rich and not too upfront, vocals are clear and full of emotion.
Second Hand News – The song sound great here, not compressed in any way. Guitar in the background is lovely, and the vocals sound as good as ever.
Symphony No. 9 – I won’t go into all the details, but this is a marvelous match up – the way a real orchestra should sound.
Sweet Georgia Brown – You can really delve into all the nuances of this audiophile recording. Not to mention the soundstage and imaging is amazing here. Cymbals sound excellent, trumpets sound a bit harsh, but that’s partially due to this recording, and partially due to the bright nature of the RS1e.
Grado GS1000e:
Sweet Georgia Brown – Drums are spot on, and this song seems to have “impact” now. Separation is really nice, and everything is incredibly accurate. Welcome to the audiophile world. 

Peel me a Grape – The vocals are still a bit sharp (due to the Grado sound), but the bass here is nice and extended, and the detail is effortlessly in front of you; you don’t have to go looking for it.
Uoon 1 – The bass here is very nice and extended, and the song sings now.
I’ve tested this headphone with many other songs, though there’s not much else to say. They all follow the same trend – rich bass (though not planar magnetic quality), extremely detailed, transparent, and very accurate; but there’s sometimes bright highs. I’m not such a fan of this headphone to begin with, but I can see from this pairing how someone might be. This pairing doesn’t leave anything else out for another DAC/amp to fill, in my opinion.
Beyerdynamic T90:
The T90 is a very analytical headphone, so paired with the m9XX, some may feel it needs some warmth, which the m9XX understandably doesn’t provide – the m9XX is more neutral than anything. However, this pairing is strong on all its technical aspects, though I can’t help but feel that the T90 would really benefit from a warm amplifier like the Beyerdynamic A20. Detail and imaging are very high throughout every song I listened to though, and for critical listening tests, it’s a very good pairing.
The Search for Ambrosia – Sub-bass is lacking a bit, although the detail is very good here and spot on.
Uoon I – Detail is better here than with the other headphones I’ve tried, probably due to the T90’s resolving nature. Sub-bass is present here, although it does seem a little left back. The song is very enjoyable, but it does seem a little technical.
Set Fire to the Rain – Pianos are great here, and so are vocals. This pairing seems to be really nice with this song.
The Woven Web – Guitars sound a bit thin, although it handles the speed of the song very well, and is very detailed.
Beyerdynamic T1 2nd generation:
There’s a lot this pairing has to offer, although I can imagine a better pairing. Be careful when using songs with deep bass, as this will go so low it will start echoing back at you a little bit. Soundstage disappoints here, and I would probably suggest (ideally, anyway) a tube amp to bring out the richness in the sound; it seems that it would go better with the T1.
Uoon I – Piano is very accurate, and smooth. Sub-bass is also smooth and very nice sounding. Highs aren’t tame, but are a bit smooth, not forward.
Peel me a Grape – I’m seeing a trend here now, the T1 makes everything smooth while keeping the detail, which comes really in handy in this song.
Aja – separation is very good, and sub-bass is nice, clean and extended once again. It’s easy to get into the groove of this song.
A New Challenger – It’s scary how deep the bass goes here, to the point I even here the echo/rumble. Extremely clear. The m9XX leaves nothing out here.
The Search for Ambrosia – 1:56 seems to get a tad muddy, although this is talking about compared to an ideally perfect sound. Other than that, highs, mids and lows, are spot on and top notch.
Mai Nozipo – Drums sound good here, but again with a bit of the echo/rumble I talked about before. Violins aren’t bright or in your face,
Set Fire to the Rain: Vocals here are a real treat, and imaging is freakishly good, especially the background sounds.
Juggling Molecules: Soundstage here is a bit small for my liking, and this song is usually the one I use to test for soundstage. A bit disappointed in that regard.
m9XX’s amplifier compared to the Beyerdynamic A20 (a $600 standalone amplifier):
The A20 at $600 seems to drive the T1 2nd generation better than the m9XX does.  Soundstage has improved, and the bass response is better. The sound becomes a bit warmer, and vocals seem more natural, and fuller. This isn’t too much of a surprise, as the both the headphone and the amplifier are made by Beyerdynamic (thus made for each other). The A20 is also a hundred dollars more, as well as only an amp (vs. the m9XX’s DAC/amp capabilities and features), so I wasn’t too surprised when the A20 was a better match. However, in this pairing, the m9XX isn’t too far behind.
With the HE-400i, however, I enjoyed it much more with the m9XX – with the A20, it’s more tame and dry. You simply don’t get to see the planar magnetic bass qualities of this headphone. The m9XX though, is a fantastic match for it, and drives the bass very well here. Vocals are almost a tie, with the m9XX being slightly better in detail and tonality.
So surprisingly, the A20 isn’t miles ahead of the m9XX – despite being much bigger, more expensive, and only an amplifier. In fact, the m9XX is a much better match with the HE-400i than the A20 is. This leads me to believe that the A20 is tuned for Beyerdynamic headphones, and for other headphones (especially planar magnetics) the m9XX will drive them better.
DAC/amp Comparisons:
m9XX vs Nuforce uDAC-2:
Highs are harsher on the uDAC-2, and things seem more clustered. Separation isn’t that great, and songs feel like a wall of sound compared to the m9XX. Detail is worse on the uDAC. Bass extends lower on the uDAC, but is muddy compared to the m9XX. All but the best recorded vocals seem flat on the uDAC, but that’s every headphone paired with it, nothing new there.
Switching over to the m9XX, everything seems more natural, especially vocals and drums. Bass becomes cleaner, and the song feels more 3D-like. Details become more noticeable, and every song sounds a lot more like it should.
Is there a difference between the two? Absolutely; there's a very noticeable difference between the two DAC/amp's, and the m9XX is definitely seen as an upgrade.
m9XX vs. CEntrance DACport Slim:
On the Slim, songs feel a lot more forward (a bit too much, in my opinion), and doesn’t really do well in terms of soundstage. Sub-bass, while not muddy, is bloated on the Slim. Very noticeable in “Mai Nozipo” (Pieces of Africa) where the drums feel very unnatural and unnecessary bloated – it takes over the entire frequency, and I can’t really hear anything else. Vocals, while pleasant, are a definite step down from the m9XX, can be a bit harsh at times, and aren’t detailed at all. Resolution is worse on the Slim, although it does put in a good effort for its price.
Conclusion: Although the DACport Slim is an amazing DAC/amp for the price, it can’t nearly compete with the detail of the m9XX. The Slim’s sub-bass alone makes me want to switch over to the m9XX, and clarity is much better on the m9XX. Is there a difference between the two? Absolutely, and it’s not even close. While the Slim is a fabulous match for the K7XX tonality-wise, the m9XX is simply better in every way, even with the K7XX.
m9XX vs. Tralucent DacAmp One ($400 portable DAC/amp):
Conclusion: The DacAmp One has a Sabre DAC – and it really shows in the detail here. It’s definitely a closer call between these two than the others, but the m9XX wins in the end – the DacAmp One seems cold and technical compared to the m9XX, and not nearly as musical. The m9XX also offers slightly more details, both macro and micro, has a much larger soundstage, and provides better imaging. The DacAmp One has more treble, although it does seem a bit too unnaturally “crisp”. Is there a difference between the two? Yes, although it did take me a few songs to pinpoint exactly what those differences were, aside from the soundstage. Listening to both for extended amount of times though, I definitely like the m9XX’s sound better, and believe it is a worthwhile upgrade that will definitely be noticeable in the long run.
$500 is not pocket change – it’s mid-tier for audio equipment, and a big investment. However, in terms of sound, it punches much higher than its price bracket. The m9XX simply brings a lot more detail, clarity, and accuracy to the table than all the other “budget” offerings I’ve heard (Aune X1S, ODAC/O2, Schiit Stack, etc.), and even compared to DAC/amps similarly priced to the m9XX it does very well.
The m9XX has many features that other DAC/amps in the mid-tier category leave out. It has a display, two headphone outputs, anti-aliasing filters, and many more that aren’t usually included in this price range. The m9XX is not only a desktop solution – it also has a portable option, and is quite small. Neither the ODAC/O2 combo, Schiit stack, or Aune X1S are portable by any means, and the first two aren’t much of an option for IEM’s and CIEM’s either. In addition to sounding very good with IEM’s, it was nearly dead silent with the hiss-prone DN-2000J until the 90th volume step.
In terms of driving full-sized cans, it had enough power for anything I threw at it, doing very well with both the 470 ohm Audio Technica ATH-R70x, and the 600 ohm Beyerdynamic T1.
Driving power is fantastic, and much better than I was expecting from the physical size of the m9XX.
So should you get it? If you have enough room in your budget to buy the m9XX, I would say yes, provided that your headphone pairs well with it. Common sense and Google should tell you if your headphone pairs exclusively well with a tube amp, and in that case every solid-state DAC/amp should be off your radar. I wouldn’t skimp out and by an ODAC combo or the X1S unless it’s specifically known to pair well with your headphone - there’s a large difference between the m9XX and the budget DAC/amps, all of which I liked a lot until I heard the m9XX.
To me, the m9XX is an upgrade that is well worth its price – the HE400i sounds better than I have ever heard it, and the K7XX is on a whole new level with this pairing. Even moving up to the higher-priced headphones, it paired well with all but the Beyerdynamic T1. Considering its versatility and all that it has to offer, the m9XX is one DAC/amp I wouldn’t want to miss out on.
- Avishai Zitron
Does anyone know where the Grace is manufactured?
Tony in Michigan
Bro, the grass shots. lol


Grand Master Moe "G"….Don't crossface me, bro!
Ping Pong Champ: SF Meet (2016,2017), CanJams (London 2016, RMAF 2016, NYC 2017, SoCal 2017, RMAF 2017)
Pros: Glorious sound, clarity, transparency, small, yet powerful, do not need power outlet to run.
Cons: Limited to 500 (for now at least), make sure to get yours now! Other than that, nothing else.
Review: Grace Design x Massdrop m9XX DAC/Amp
Have you ever experienced a day where you knew it went well, but did not know how much of an effect that day would have on your life? This was the case the day that I spoke with Massdrop's Will Bright about a couple of amp-type products that they were going to launch in the near future. One was a small (very small), but powerful DAC/amp called the CEntrance DACport Slim, and the other was an amp that was from the Colorado, United States-based company Grace Design.  I have conversed with Will on multiple occasions and in person, and I can comfortably say that his collaborations are exemplary and intriguing.  Usually what he likes, I like as well.  This comes back to the days (not too long ago), when all that we talked about were our Shure SE846 earphones with vigor and excitement.   Wanting to learn more about Grace Design and amplification in general, I graciously accepted the offer to share my opinion.  I have experience with most aspects of high-fidelity audio, but haven’t owned any significant DAC/amp in my life.  This was until I received a box with the words “GRACE DESIGN” ablaze on it.  Curious to find out what was inside, I opened it up.  My jaw dropped and my eyes widened.  Behold…
The Grace Design x Massdrop m9XX DAC/Amp
Clockwise starting at upper-left:  USB type A to USB type B micro cable 6', 2A power adapter,  USB type A to USB type B micro cables 10', m9XX

Front of m9XX

Front of m9XX

Volume control rotary encoder

Rear of m9XX

Underside of m9XX

Audio equipment used in the review
CEntrance DACport Slim: $99 shipped in the United States
Grace Design x Massdrop m9XX DAC/Amp: $499 shipped in the United States
HIFIMAN HE1000: $2,999
Master & Dynamic MH30: $349
Master & Dynamic MH40: $399
Sennheiser Momentum 2.0 AEi: $349.95
Puro Sound Labs IEM500: $199.99
Sennheiser Momentum In-Ear: $99.95
Shure SE846: $1,000
Sensaphonics Custom Sleeves: $150 (used with Shure SE846)
Third-party cable
Headphone Lounge FBI Reference Silver Litz Cable (MMCX) = Price varies
iPhone 6 (Space Gray, 128GB):  $849.99 or $399.99 with a 2-Year Contract
Questyle Audio QP1R Golden and Space Gray: $899 USD
Samsung S5 (Shimmery White): $552.00 with Verizon
Software Applications Used
JRiver Media Center 20: $49.98
Sound Level Analyzer: $4.99
TIDAL HiFi – Lossless: $20 per month or $10 with student discount
Adapter for 1/4 inch headphone inputs
iMBAPrice Premium High Quality Adapter STEREO GOLD Plug 1/4" (6.3mm) Male to 1/8" (3.5mm) Female - Gold Plated - Lifetime Warranty (I use a similar adapter): $5.09
If you have read my earlier Head-Fi posts (mostly in the Shure SE846 Impressions Thread), I say that the iPhone is enough for an IEM, and that I am in no need for a DAC/amp.  Being able to attend various meets and listening to a plethora of awesome sounding DAC/amps, my position started to change slightly.  I still feel that an iPhone sounds great.  However, having that extra kick, clarity and overall audio coherency that a properly implemented DAC/amp can provide is paramount.  This is especially true when you are dealing with the task of driving less efficient headphones. 
I would like to share my experience with the m9XX over the time that I have been able to own this graceful, yet powerful DAC/amp.
I feel that since there are only 500 units being dropped on Massdrop here:, I should explain why you should purchase this DAC/amp.  This is one of my favorite sounding DAC/amps regardless of form-factor and price that I have listened to.  Once you factor in the form-factor, price that is not exorbitant, as well as the exclusivity of owning a limited-run (possibly) device, you owe it to yourself to give the DAC/amp a shot – not just a listen…but a purchase.  What’s great is that you can buy the m9XX and not love it.  You can then give the m9XX to a friend, family member or audiophile/music lover as a gift, and as a result, they will adore the sound that the Grace Design DAC/amp effortlessly produces.  I call the m9XX a “Portable Desktop Solution”, or “PDS”, respectably.
More about the PDS moniker, why call it that? 
Portable – powers IEMs with the linear volume selection, meaning from “0.” (or ½/.5) to about 50 (with a sensitive IEM such as the Shure SE846) the volume rises very gradually.  The m9XX powers most all headphones with some serious power at the higher numbers.
Desktop – emits a dedicated desktop/quality (or better) sound, which is amazing for its miniscule dimensions.  Headphones get VIP treatment, and IEMs get VIP treatment as well, as both are taken care of with the utmost of affection.
Solution – this is a portable desktop solution for higher powered phones like the Samsung S5, computers, or anything that utilizes a lineout or optical out.  The solution is an immensely high-fidelity sound in the palm of your hand that you can transport, and as a result, is simply marvelous.
Let's get connected
When I first connected the m9XX, I got absolutely no volume from my HE1000.  What I did not know until I realized after a few minutes, was that even having the volume at “40” does not do much good for the average difficulty to drive HE1000.  The volume stays at a low volume up to about “50” for sensitive IEMs, which is an amazing feature the m9XX offers.  I usually keep the volume low when listening to a DAC/amp for the first time, since I have experience with volumes higher than normal when I try out the DAC/amp for the first time (for instance, listening at a meet), so having the volume very low, and turning it up was not helping at all.  As soon as I “went for it” and turned it up to the 70’s and 80’s, did I start to hear any substantial volume.  Once I was able to hear the music, the volume escalates very quickly, and with aplomb.  The m9XX is able to power difficult to drive headphones, as it has more power than my QP1R (which does well with difficult to drive headphones) and the DACport Slim (which also powers headphones well despite its diminutive size).
Keep the music playing
As mentioned in the manual, if you connect and sometimes disconnect the headphone from the m9XX while music is playing, the m9XX will show “OC”, which means “Over Current”.  The internal processor will mute the audio and momentarily shut down the audio supplies to protect the m9XX from damage and to also keep the m9XX from drawing excessive current from your computer.  When the m9XX shows “OC”, the volume will be muted for several seconds, and then will turn back on.
I experienced "OC" during these situations:
  1. Unplugging/plugging in earphones/headphones at higher volumes.
  2. Anytime the m9XX was playing at a high volume at approximately 90s and higher with headphones plugged in (never tried with earphones because anything “90” and above can damage the earphones since the volume output is exceedingly loud).
  3. Using only the USB input from a computer will cause the m9XX to “OC” while very loud music is playing at approximately 90 and higher (Low Power mode).  Adding in the external power source (via “5V, 2A" USB input – High Power mode) allowed the m9XX to reach the entire volume range (“99.”) with ease and does not “OC”.
  4. Muting the volume before plugging and unplugging in the headphones/earphones during Low and High Power modes made it so I would not experience “OC” at all.
Higher power devices should work
I tried to get my iPhone 6 connected to the m9XX via Apple CCK, USB hub and outlet power/external battery charger, to no avail (keep reading, solution below):
However, I spoke with a m9XX owner and friend @HiFiGuy528, and he was able to get his iOS devices (iPhone 6 and 6+, etc.) working with his Cute USB 2-port hub!  It can be purchased here:  I purchased one in black, and it arrived and works with the iPhone 6 without any issue.  Here's the setup:
Cute USB Mini 2-port USB 2.0 Hub Splitter

Side view

Showing 2 USB ports

Connected to Apple CCK
iPhone 6 to Apple CCK to Cute USB Mini to USB A/USB B to USB input; USB A/USB B to power outlet

iPhone 6 to Apple CCK to Cute USB Mini to USB A/USB B to USB input; USB A/USB B to external battery charger (Anker PowerCore+ 13400mAh external battery charger shown)

Close-up angle of same connection above

Connection updateWith the 0008_DFU m9XX firmware update, I was not only able to get the iPhone 6 to connect on it's own (via power source as well), without the need of a USB add-on such as the Cute USB Mini 2-port Hub, but I was able to get the m9XX (using Windows 7 Ultimate) to set as the default automatically when it's plugged in each time!  Very happy with the update:
iPhone 6 to Apple CCK to USB A/USB B to USB input; USB A/USB B to external battery charger (Anker PowerCore+ 13400mAh external battery charger shown) and IEM500

iPhone 6 to Apple CCK to USB A/USB B to USB input; USB A/USB B to external battery charger (Anker PowerCore+ 13400mAh external battery charger shown) and HE1000

I was able to get my friend and Head-Fier @Netforce's Samsung S5 working via S5, USB to USB mini cable and external battery charger:

TOSLINK optical input
I wanted to see how optical would fare with the m9XX, so I connected the QP1R to the m9XX optically, using a TOSLINK optical adapter with the optical cable for the QP1R, connected to the m9XX.
TOSLINK optical cable adapter and optical cable

TOSLINK optical adapter connected to optical cable

TOSLINK optical connected to QP1R
TOSLINK optical from QP1R connected to m9XX
“Dropped” Massdrop m9XX’s will have the updated firmware that will silence the music when a file over a 96kHz PCM digital audio signal attempts to play via optical.
The sound from the HE1000, QP1R and m9XX was sublime, and was highly resolute and utterly transparent.  I would say the presentation was such a rewarding experience that you would want to listen to just one more track.
Family game night
I brought some of my audio equipment for my family to listen to. 

The only person to listen to the m9XX that night was my younger brother. 
My brother listening to JRiver + HE1000 + m9XX

My brother is interested in video games, computers and music, but not necessarily higher-fidelity or more expensive equipment.  He was game to listen to the m9XX and share with me (and now, you) his thoughts.
Here's my brother's thoughts after listening to a few tracks from Tidal, HE1000 and m9XX:  “Very crisp and clear.  You know the “Five” gum commercial?  You are surrounded by the vibrations, and it feels like you are there.  It feels like you are surrounded by the music.” 
After listening to Logic – Like Woah via Tidal, Sennheiser Momentum 2.0 AEi and m9XX, he said it sounds like digital surround.  He says he that can hear the drums behind him. 
Next up is the MH40 same track – he says it sounds almost like the Momentum – good!
Finally he takes a listen to the MH30 – he likes the bass on these. “One thing that stood out was the bass. It really stands out. Good sound. More compact than the others.”
Great, now let’s go for a comparison.  I played a song that was melodic, popular, and just a fun listen for my brother to make comparisons – Kings Never Die from Eminem and Gwen Stefani.  He listened to both the m9XX and QP1R on the Momentum 2.0 AEi, playing the same track at around the same volume, calibrated via Sound Level Analyzer.  He preferred the Grace Design amp sound compared to the Questyle player’s sound. He said the Momentum 2.0 AEi's sound with the m9XX sounded very quiet and said with the QP1R it sounds like you know you are wearing headphones. 
Next up, the HE1000 is ready for the comparison.  He says that there isn’t as much interference or background noise with the m9XX than the QP1R has. He articulates: “You know when you are shopping for TV's and the color black that is blacker determines the better TV, same way with the sound of the music as well. When there is more silence on the quieter parts the better it sounds. With the amp I think it sounds pitch black with regards to background noise.” 
Ray Charles & Count Basie Orchestra - Oh What a Beautiful Morning is the next track that is being compared that sounded amazingly graceful (no pun intended, or maybe, who knows?) with the HE1000 and Grace Design DAC/amp.  The next song that I played was a 320kb song, Ed Sheeran's Bloodstream, and my brother thought it sounded great. He iterates: “Sounds so good for being a lossy file. Can easily mistake it for a song of a higher bitrate. Very clear.” 
Overall, my brother thinks that the DAC/amp is worth it for the price for audiophiles. 
Notable features
Low and High Power modes, which is great because you do not have to depend solely on High Power mode/outlet power, as using Low Power mode/USB and an external battery charger makes the m9XX truly portable.
The TOSLINK optical and RCA output gives you another way to enjoy your music – via power amp or powered speakers which is always welcome.
Two headphone outputs makes it so you and a friend can listen to the same song.  What I do if I know there is a “mismatch” with a headphone/earphone such as one requires more volume than the other; I will only match near efficient pairs.  For example, I can pair the easy to drive Sennheiser Momentum 2.0 AEi with the very easy to drive Shure SE846 in respectable inputs.  I can also pair a little bit more difficult to drive HE1000 with the more difficult to drive IEM500 in respectable inputs.
Crossfeed circuitry is a welcome option as it can be turned on or off. I keep the crossfeed on.
The volume control is the overall best looking and feeling rotary encoder that I have ever felt.  This is the truth.  The volume control is the truth.  The tactile feedback is immeasurably satisfying.  You turn the rotary encoder either way to turn up or down the volume.  You press it down with a satisfying “click” sound to mute the audio (and negate ever experiencing “OC”!)  Once you keep the rotary encoder down for two seconds, you will enter the m9XX’s options, turning the rotary encoder either way to change the settings or press down the rotary encoder to change the selected setting.
The 7-segment display is bright, large enough and easily legible in bright light as well as complete darkness.  You also have the option to turn off the illumination via “Display Dimmer Mode” setting (d.d. [dim] or dd [not active]).
The power up level is a thought out option; because you can set exactly what volume step you want the m9XX to start up every time.  I keep mine at “0” when it powers up.
The DAC filter utilizes four filter response modes, which are:
F1 = Sharp roll off, linear phase
F2 = Slow roll off, linear phase
F3 = Sharp roll off, minimum phase
F4 = Slow roll off, minimum phase
Here's more information regarding the filters:
To read more about the AK4490 DAC, you can peruse through this link:
I chose the default, which is the F1 = Sharp roll off, linear phase filter response mode.
0.08 Ω of output impedance – black backgrounds are par for the course.
The chassis and every part of the m9XX are made with high quality anodized aluminum and steel what looks to me like aircraft-quality materials.  Yes, it looks and feels that wonderful.
Power comparisons
My method of dB reading:
  • Perform tests in a quiet room or as quiet area as possible.
  • Set Sound Level Analyzer (Z frequency weighted) settings.
  • Use stock cables for tests.
  • Place microphone of iPhone 6 very close to the left earcup on all tests.
  • Make sure earcup is open and not laying on an object.
  • Run DAC/port Slim and m9XX at full volume (High gain, "90.").
  • Use -3 dBFS 192 kHz pink noise track.
  • A screenshot is taken of Sound Level Analyzer's "Lmin (dB)", "Leq (dB)" and "Lmax (dB)".
All measurements have been created with no EQ utilized.
I calibrated both DAC/port Slim and m9XX to emit the HE1000 around 81 dB with the Sound Level Analyzer (Z frequency weighted) as both DAC/amps were loaded with the same -3 dBFS 192 kHz pink noise track for sound quality comparison tests.  The HE1000 + DACport Slim needed about 1 1/2 full volume dial sliding upwards on High Gain and the HE1000 + m9XX needed "82." to reach as approximate the same sound level/volume as possible. 
Max volume of the DACport Slim and HE1000 using Sound Level Analyzer (Z weighting) and -3 dBFS 192 kHz pink noise track
m9XX + HE1000 with 1/4 to 1/8 in adapter
m9XX + HE1000 with 1/4 in cable
Sound impressions
I think the sound of the Grace Design DAC/amp is balanced and not overly or artificially boosted in any area of the frequency spectrum. The transparency of the presentation is apparent and immediate. It reminds me of food that tastes so invigorating, but hits the spot, is not too sour, not too salty, not too sweet, and not too spicy.  It tastes just right.  Compared to the DACport Slim, the m9XX is more coherent, resolving, clear and is able to retrieve micro, macro, and major detail in a more preferable manner.  The DACport Slim has more overall bass in its presentation, and the m9XX is more balanced and natural in its presentation. 
Disclaimer and hearing factors
The earphone and headphone reviews (brief or more in-depth) are mainly for anyone wanting a point of reference regarding how they more or less pair with the m9XX. 
We all hear differently, and our experiences with regards to how our interpretation of what we hear vary greatly.  Some factors that come to mind (and not limited), are: 
Your inner ear and skull’s overall composition:
Hearing loss as we age, also known as presbycusis,
Heredity, noise trauma, dietary habits, smoking, hypertension, atherosclerosis, are other factors that affect people’s overall hearing ability.
Select headphone/IEM pairings
Shure SE846 + SCS 

Tight.  Punchy.  Spacious.  Immersive!  The SE846 is a fabulous combination with the m9XX.  I personally do not detect a low treble rolloff.  I am using the SCS + Ted’s Silver Litz, plus black filter mod/white filter, so those mods/add-ons/replacements more than likely contribute to the veil of sorts being lifted.  Wow…wow.  I am listening to Seal’s Life On The Dance Floor via Tidal and m9XX, and it sounds so sweet and resolving.  Every bit of the sound spectrum, be it bass, midrange, treble, spatial capabilities simply ceases to amaze me.  The SE846 + SCS + m9XX are coherent and resolving without clutter, without mess.  I can go on and on, but this combination is a winner for those that want a clear and coherent sound with the extra bass kick for good measure.
Puro Sound Labs IEM500

When I met Jim Noyd at The Source A/V meet not too long ago, I just thought he would let me listen to the IEM500 as it looked pretty good on their website.  He gave them to me.  No mention of giving a review on them.  I wouldn’t have either more than likely if I didn’t like them, but these IEMs sound so lovely, that it would be a disservice not to say anything publicly about them.  A review will more than likely be forthcoming, but I need to say some thoughts about how they pair with the m9XX.  In one word: lush.  The overall sound is very rich, and I can tell the double dynamic drivers are working in full unison.  The bass is obvious, but not overbearing.  The midrange is liquid smooth, more like a vanilla shake from In-N-Out.  If too many food references are getting to you, let me know – but these foods are what comes to my mind.  The treble is laid-back and not harsh in the least.  The spatial capabilities, mainly soundstage, imaging and detail retrieval, are natural and present.  Intimate, yet spacious, are the words I would describe the IEM500 and m9XX combination.  Worth a listen, and worth purchasing, as I saw the prices of these on Amazon – wow!
Sennheiser Momentum In-Ear

This is the world premiere Momentum In-Ear in black chrome.  When I first listened to Jude’s maroon colored Momentum In-Ear for the first time, I asked him “How many drivers are in this?”  He said “Just one”.  I replied “Wow, I’ve got to get me one of these!” Thank you to Mr. Mahmood for supplying me with an IEM that I liked from the start, in exchange for my opinion.  I am simply enamored by this mighty single dynamic driver IEM.  I loved the maroon color of the original Momentum, but Sennheiser has hit it out of the park with a blingy, yet classy iteration of the popular Momentum In-Ear.  The m9XX turns this into a more balanced IEM.  The prominent midbass presentation still remains, but what a sublime midbass the Momentum In-Ear emits.  The entire presentation is warm, but gooey, like a tasty Cinnabon.  If you haven’t experienced a Cinnabon yet, you need to.  Okay, back to the fabulous sounding Momentum In-Ear.  The tonal balance of the midrange and treble is detailed, yet suave all at the same time.  Soundstage and imaging are not the strongest suits, but the crossfeed of the m9XX does an exemplary job of making the spatial capabilities of the Momentum In-Ear blossom to the best of its abilities. A great listen and warm sounding IEM, but opens up when paired with the m9XX.
Sennheiser Momentum 2.0 AEi

This headphone is already balanced and dignified via an iPhone.  Paired with the m9XX, the Momentum 2.0 AEi is a capable headphone.  I would like to thank Mr. Mahmood for sending over the brown version to me for my honest opinion.  What I like is the cups actually look like a dark metallic bronze color, very subtle, yet stylish.  If you check my earlier posts on Head-Fi, I posted that I did not like the original Momentum’s sound.  The update is more my cup of tea, to say the least.  I will not say exactly which headphone Sennheiser I do not like as much as the Momentum 2.0 AEi, but what I will say is that this headphone is relatively new, and I thought that I would like the headphone it since the description on paper seemed like something I may thoroughly enjoy.  Not quite.  This is okay, because the Momentum 2.0 AEi is cheaper than the particular headphone, and seems to be more of a coherent sounding headphone as well.  What I couldn’t have imagined is how much it would be liked by the people that have listened to it.  Against the MH30 and MH40, it was my fiancée as well as my brother’s favorite headphone.
There is a hint of midbass lift, but not nearly the amount of the Momentum In-Ear, for comparison.  The m9XX opens up the warmth in a meaningful manner.  The bass is tight and controlled, with not a lot of overhang.  The midrange – you can feel the texture, smooth like a rock that has been formed by the constant waves of the ocean.  The treble is easy-going, and should never be a concern with regards to fatigue.  The soundstage and imaging has opened, gotten better, like a wine that has been aged for 20 years, yet this transformation simply took a connection to the m9XX.  The Momentum 2.0 AEi is a thoroughly engaging involvement with the m9XX.

If I could describe what I am hearing with the HE1000 +Tidal + m9XX while listening to R.City’s Like This and R.City / Adam Levine’s Locked Away in one sentence, it would be the HE1000 is the personification of highly detailed, eerily spacious, utterly present transparency that is resolute and is effortlessly an immensely fine listen.  I am highly fortunate and grateful to have the ability to own this setup, and share it with whomever I meet in the world.
Closing remarks
Thanks to Grace Design for creating such an awesome DAC/amp and thanks to Will Bright and Massdrop for offering it at such an attainable price.  Thanks to @jude for not only bringing the glorious Grace Design x Massdrop DAC/Amp to our attention, but I would like to thank him for everything that he has done with regards to bringing the world of music and people together, one conversation at a time.
Thank you for reading, I appreciate every last one of you.
Grace Design x Massdrop m9XX DAC/Amp Specifications
THD+N at Maximum Volume, 1kHz, 22Hz-22kHz BW
0dBFS In, +14dBV Out = <0.002%
Intermodulation Distortion SMTPE/DIN 4:1 50Hz, 7kHz
@1.0V out, no load = <0.008%
@1.0V out, 32 Ω load = <0.009%
Frequency Response +/-3dB
Fs=96kHz = 0.5-45.9kHz
Dynamic Range
20-22kHz bandwidth = 112dB
20-22kHz bandwidth and A weighting filter = 115dB
Output Noise
20-22kHz, volume=0-90 = -106dBV
A weighting filter, volume = 0-90 = -109dBV
20-22kHz, volume=90.5-99.5 = -96dBV
A weighting filter, volume = 90.5-99.5 = -98dBV
100Hz = <107dB
1kHz = <98dB
20kHz = <72dB
Attenuation Range = 0 to -99dB, 0.5dB steps
Channel Tracking Accuracy = +/-0.05dB
Maximum Output Level = +14dBV (5.1V)
Headphone Output = 0.08 Ω
Line Output 47.5 = Ω
1kHz, -1dBFS, (0dBFS = +20dBu), 20-22kHz bandwidth = 0.0006%
Dynamic Range
20-22kHz bandwidth, 0dBFS = +20dBu (AES17 filter) = 117dB
20-22kHz bandwidth, 0dBFS = +20dBu (A-weighted) = 119dB
Input Lock Range
TOSLINK = 96kHz +/-1300Hz
USB = 44.1, 48, 88.2, 96, 176.4, 192kHz
Power Consumption
Max, High Power mode = 8.0W
Max, Low Power mode = 2.5W
Dimensions = 4” x 5.25” x 1.8”
Headphone Output Power
Low Power ModeOutput Power mWOutput Power mW
Load Resistance Ohms1 Channel Driven2 Channels Driven
High Power ModeOutput Power mWOutput Power mW
Load Resistance Ohms1 Channel Driven2 Channels Driven
Thanks for the review! Good read. 
Pedro Retador
Pedro Retador
I have a little and simple question. Does the Sennheiser Momentum's 2.0 pair well with the Dacport Slim? These are very low impedance headphones, for one side, and are considered warm. So, ¿do they make a good marriage? Thanks in advance.


Headphoneus Supremus
Pros: Balanced, transparent sound without being clinical or dry, excellent build quality, highly intuitive controls, powerful headphone amp
Cons: Initially limited to 500 units so it might be hard to get once they sell out

Nowadays, there's more headphone-oriented gear on the market than you can shake a stick at. Headphones are abundant. Headphone amps come in a wide variety of styles, prices, and topographies. And plenty of DACs now feature quality onboard headphone amplification. It's a headphone lover's dream.

Things were not always this way. Go back about 10 year, and there was far less of.... everything. In particular, if you wanted a quality all-in-one DAC/headamp solution, choices were rather limited. The major contenders came not from audiophile brands but rather the pro audio world. We had the Benchmark DAC 1, the Lavry DA10, the Grace Design Model 901, and - to a lesser extent - the Apogee Mini DAC. All offered what was considered at the time to be exceptional D/A conversion, with at least a reasonably nice headphone output, in a decidedly pro-audio oriented package. And the price on most of these approached $1k which was not a small sum back then. The Grace Design unit set itself apart by selling for $1,500 and by referring to itself primarily as a headphone amp - D/A conversion was also part of the deal, but the lack of analog outputs meant headphones were the only way to listen.

At the time, I cycled through all four models in my search for headphone bliss. I quickly eliminated the Apogee as being sub-par compared to the trio of Grace, Benchmark, and Lavry. All three models had their strengths and weaknesses, such that I enjoyed them all in their own way. This was a hot topic on forums at the time. It seems like many headphone enthusiasts were coming to the same conclusions I was: the Benchmark was crazy detailed but somewhat bright and unforgiving. The Lavry was creamy smooth and could be described as the most "analog" sounding. The Grace was perhaps the most balanced of the lot. All three models had their fans and a few detractors too, as is usually the case with most gear.

The m901 was my favorite option for driving my reference headphones, which at the time consisted of models like the Audio Technica L3000, Grado RS-1, and of course the Sennheiser HD600 which was standard issue for enthusiasts back then (and probably still should be). I wasn't in love with the 901's DAC portion, but the headphone stage was phenomenal. I often paired the Lavry as DAC with the Grace as amp, playing to the strengths of each model. Then along came the Grace m902 which I felt significantly improved the DAC section. While perhaps still lagging slightly behind the Lavry, it was close enough for me to sell the DA10 and stick with a one box solution for a time. It was also novel in having a USB input with which I took my first steps in computer audio. Very few devices had USB inputs at that time. But as other stuff hit the market I eventually moved on - you know how it goes. Grace had success with their m903 and more recently the m920, both of which seemed competitive in their field. I have heard both but not extensively. My point is, Grace Design has made catering to us headphone enthusiasts a priority for over a decade by now, so they have some expertise on the subject.

The range between $1,000 and $2,000 is jam packed with killer DAC/headphone amp combos. I'd say that's probably where you'll find the best value, in terms of gear that approaches state of the art but doesn't cost more than a new car. As you drop lower than that, it becomes more of an exercise in priorities. I'm not saying there aren't some solid devices out there. There's just usually some sacrifice involved. Maybe the headphone out isn't all that great. Maybe the USB implementation isn't on par with the alternatives. Maybe the amp does great with full size cans but doesn't play well with IEMs, or maybe it's the other way around. The trick is figuring out how to minimize weaknesses while packing in all the stuff us HeadFiers want most. Not a lot of devices nail those objectives.

One option, however, recently made its way to my audio rack, and it's worth talking about - the Grace Design m9XX. The product of a joint venture between Grace Design and Massdrop, the m9XX will go for $499 and should be available to order in a few days. It's a Massdrop exclusive, just like the AKG K7XX which I enjoyed so much - bonus points for sounding marvelous when paired together.

Now, for $499 I don't expect miracles from an all-in-one device. Typically we might get a pretty good DAC with a mediocre headphone amp, or vice versa. Not this time. The goal of the projects seems to have been packing most of the audio magic of the m920 (which at $1,999 is very highly regarded), stripping away many of the potentially unnecessary features, and ending up with a killer, somewhat minimalist device which performs way above its price.

While the m920 and previous generations were all half-rack sized (just like the Benchmark gear and many other popular DACs), the new m9XX is a compact little thing. At 4 inches wide, 5.25 inches deep, and less than 2 inches tall, this thing takes up very little space. Which makes it perfect for desktop duties where a larger device just wouldn't fit so well. I called the m9XX "somewhat" minimalist because, while it may lack quite a bit compared to the m920, it still has a reasonably advanced feature set considering the compact size.

Let's explore: on the input side we get XMOS-based USB capable of hi-res PCM as well as DSD64 and DSD128. There's also a Toslink input with the usual 24/96 cap. Outputs come in the form of RCA line-out as well as dual 1/4" headphone jacks, one of which automatically mutes the line-out when a headphone is inserted. Notably, Grace includes their proprietary crossfeed option for those who might find it appealing. This is a welcome feature as not many devices in this price range have the option. And Grace's crossfeed implementation has always impressed me, being less heavy handed than most - I find it particularly useful with older recordings using hard-panned mixes which clearly favor speakers over headphones, but it's subtle enough to use on modern mixes if the mood strikes. With certain headphones and music, it really does help bring the recording further "out of head", while in other cases it isn't as useful.

And that's about it. There really isn't much more room to add inputs or other options even if Grace wanted to. As it stands, they had to use micro-USB connections to save space. Yes, I said connections in the plural.... let me explain. The right side is what I'd call a "normal" USB input. It handles both power and data, allowing me to use the m9XX with my Surface Pro 3 without a mess of cables. This configuration gets us what Grace calls "low power mode" which delivers something like 160mW per channel RMS into a 32 ohm load, and roughly double that into 50 ohms. This is plenty for your Grado, Audio Technica, Ultrasone, and other sensitive headphones, and more than enough for pretty much every IEM on the planet. I also believe Grace Design is being careful not to boast using peak power, which is often done by marketing departments. If they wanted to sound more impressive they would mention the peak output for a single channel which is quite a bit higher. Need more power? That's why Grace supplies that extra USB input. By adding a second USB cable for power and using an adapter similar to a cell phone charger, the m9XX jumps up to over 1,000mW per channel at 32 ohms. Now we can run most planar magnetic headphones with very satisfying results. And with a corresponding boost in voltage we also get excellent sound with higher impedance models from Sennheiser and beyerdynamic. Again, very impressive considering the compact dimensions of this thing.

Let's talk user interaction, as I find it very well done here. The entire top of the enclosure is reserved for the multi-function knob which spins and presses to accomplish volume control and option selection. Hold it down to access the menu, which leads to options like crossfeed, startup volume memory, and 4 selectable digital filters. The display is a simple two-digit LCD with another small dot being used to indicate "on" or "off" for a function - see my pictures to help illustrate. It's a surprisingly simple yet effective system which I got the hang of immediately. The volume knob reminds me a bit of the old Ortofon HD-Q7 amp, which is quite a compliment with respect to aesthetics and usability. In fact, this entire design is somewhat reminiscent of that under appreciated little amp, which I've always felt absolutely nailed the design portion if not quite the sound quality category. The large button/knob on the m9XX is very precise, matching perfectly with the volume adjustment which is handled in .5dB increments. Overall the m9XX is a joy to use which isn't something I can say about every DAC, including some expensive models.

The heart of the DAC design is AKM's flagship AK4490 chip. This is a fairly new model, released within the last 2 years or so, and is not all that common as of yet. HeadFi folks probably recognize it most from its recent appearance in the updated Schiit Bifrost DAC where it replaces the older AK4399 used in the first gen model. It also shows up in the new (and rather expensive) Lindemann Musicbook series. Aside from those two brands, I'm not aware of anyone else using it thus far. AKM DACs in general don't seem to be used as often as Wolfson, Cirrus, TI, and ESS, so it's hard to know what to expect. Of course, the DAC chip itself is only one small piece of the puzzle, so maybe it's best we don't come into this with preconceived notions anyway.

I already mentioned the XMOS USB implementation, which ends up processing the Toslink input as well. A unique hybrid analog-digital phase-lock loop system (PLL) helps reduce jitter which is especially useful for Toslink, being more likely fed by a lesser source such as an Apple TV. Extensive power filtration is employed to make sure the noisy USB connection isn't fouling things up. Grace uses a total of 5 power supplies including separate supplies for the XMOS implementation, the DAC, and the analog stage. 5V USB power is converted and augmented by a proprietary system allowing the device to run +/- 9V rails on basic USB power, and +/- 14V when running in high power mode with the power adapter. I won't go into it too far but again this shows the expertise involved, especially for a small and relatively affordable device such as this.

The headphone output is built around a Texas Instruments THS6012 transimpedance/current feedback amplifier. I have not seen this particular chip used in this application before. More typically, we see chip amps based on either the TPA6120A2 (quite powerful but usually requires 10 ohm output impedance for stability) or the TPA6130A2 (stable at lower output impedance but far less powerful). Nothing wrong with either, but I was pleased to see something unique being used which seems to combine the best of both the TPA options. Output impedance is well below the magic 1 ohm mark - at 0.08 ohms, listeners have nothing to worry about even with IEMs sporting wacky impedance curves. And I already mentioned the output which is very robust indeed.

Now, after all that, how does the m9XX perform? In my humble opinion: it's really something special. Neutral, resolving, clean-as-a-whistle, the m9XX is an excellent monitoring tool. Paired with a nice set of active monitors, this setup allows one to hear deep into the mix, with a level of transparency few compact DACs can match. It pairs quite well with the AMT tweeter in my Adam Audio F5 monitors - a tweeter known for its expressiveness, not to mention ability to expose sources with poor timbral accuracy. Top end air and extension are without reproach, making it hard to believe this DAC/speaker combo sells for just a bit over $1k. I've heard big rigs using expensive/exotic speakers which utterly failed at reproducing the brassy tones of a trumpet, the shimmer of a crash cymbal in all its glory, or the quick attack of a piano strike The m9XX/Adam F5 combo excels in all three of these tests, proving one needn't spend a fortune to achieve lifelike sound.

Despite its clarity, I wouldn't necessarily characterize the m9XX as a clinical, dry sounding DAC. It's got enough resolution to pull out gobs of microdetail, but it also maintains a connection with the music which is lacking in many pro-audio style DACs. The result is closer to what I remember from the old Grace 901 - balanced, organic, well rounded, not lacking in detail but not shoving it down your throat either. I actually think the little m9XX would compare favorably with the original 901 in terms of DAC performance - that would be a fun comparison if I still had a 901 around. Unfortunately I don't, but I do have several more recent DAC comparisons which might help illuminate the flavor of this device.

The Parasound Zdac V2 ($549) is a very enjoyable DAC. It falls on the warm and smooth side, with a dynamic punch that may exceed what the m9XX can offer. In contrast, the Grace unit is more resolving, cleaner, and more airy in tone, with a more precise soundstage and accurate imaging. I really like both models and would choose among them based on what associated gear makes up the system.

The Rega DAC-R ($1,195) is also a warm and smooth DAC, but I find it troublesome in that it lacks the dynamic bombast of the Parasound, while going even farther into warm/smooth territory. Consequently, it feels like a wet blanket, where music just plods along with no emotion. It can be helpful for taming bright systems but that's about it. The Grace m9XX is superior in most every way, to the point of this really being no comparison. I know a few people who really enjoy what this DAC does, but I just don't hear the appeal based on extensive listening. Maybe my unit is a dud.

The Musical Fidelity MX DAC ($999) is the first Musical Fidelity product I've actually enjoyed in quite some time. I'm told there's been some restructuring at the company and some new blood brought in - hopefully this brings about good things, as Musical Fidelity used to be a big player in the headphone world with their compact X-series components. The MX is a very pleasant DAC where nothing stands out as objectionable - a good thing considering the funky performance of the previous M1 DAC and its variants. The more I listen, the more I like it, and find it very similar to their $2,500 M6 CD player I used to own - perhaps even better. By comparison, the m9XX is just as transparent, just as engaging, and at half the price, is a far better value. And that's before we consider the headphone amp functionality. Bottom line is that I really can't tell these two apart, so there's no way I'd spend double on the MF product, despite it being a very competent offering. If you needed balanced outputs or wanted to stack with the Musical Fidelity MX-HPA headphone amp, the Grace wouldn't work as well, but that's about the only situation I can think of where I wouldn't get the smaller m9XX and call it a day.

MicroMega's MyDAC, at $399, is one of the few devices here small enough to look like a direct competitor to the m9XX. Unfortunately it sounds like there were some compromises involved in achieving this small form factor and low price. It has a focus on transient attack which initially makes for an exciting sound signature, but ends up overwhelming with a busy presentation that becomes unbalanced during long term listening. This is one of those devices that you first demo and think "Wow, I love it!" but later come to hear as fatiguing. The m9XX initially seems a tad boring in comparison, with its measured, even-handed approach. Where's the bite, the snap of the music? After a short time it becomes clear that the m9XX is actually more lifelike, more organic, while the MyDAC is a neon facsimile of reality. This thing received some rave reviews a few years back, and I actually believe those reviewers were genuine in their assessments... they just threw the device in the system, listened for 20 minutes, wrote it up, and moved on. That's why I spend as much time as possible with my listening, sometimes even missing the window of new-product-buzz. I like to be confident in what I'm hearing and that sometimes takes longer than you'd expect.

$500 doesn't buy all that much performance in absolute terms... and when it does, you're typically looking at a dedicated DAC or headphone amp by itself rather than a combo unit like this. So how about that headphone output - is it compromised as we might expect for the price? Thankfully, no. The m9XX sounds very satisfying driving headphones directly. Just like the DAC portion, it strikes an excellent balance between accuracy and musicality, and pairs well with nearly every headphone I have on hand. I'm actually rather surprised at how well it does considering the size of this little box. Apparently Grace knows their stuff.

Straight from a single USB connection which translates to low power mode, the headphone out is exceptional with IEMs. I get a mild, very tolerable hiss with my EarWerkz Supra, JH13 FreqPhase, and Unique Melody Merlin, which my brain easily filters out once the music starts. The rest of the IEMs in my collection play with an essentially silent background: Noble Audio K10, 5C, 4C, and Savant, Dunu Titan, Lear LCM-5 and LCM-BD4.2, the Aurisonics AS-1b, and many others which I'm forgetting at the moment. A volume setting of roughly 50 (out of 99) is typically good for most music, leaving plenty of room to dial in more or less as needed. I'm a huge fan of custom IEMs and it can be frustrating when so many amps - somewhat counter intuitively - can't handle these easy-to-drive little things. I'm happy to report the m9XX passes the test with flying colors. A top-level CIEM can be as resolving (arguably more so) than the best full size headphones, and will often expose weaknesses in a source. Again, the m9XX passes the test with aplomb.

Moving to full-size headphones, the m9XX does a very competent job as well. As I mentioned earlier, some models do just fine in low power mode. The Astell & Kern AK T5P, a rather sensitive flagship closed back headphone, is extremely enjoyable with the m9XX set to volume 60-70. If this was my main headphone I wouldn't ever use the high power mode. Same with the Grado PS500 and the Sony MDR-1A. Of course, driving current-hungry planar magnetic cans like the Audeze LCD-2 provides an obvious excuse to run that second USB cable with the power adapter. Note that gain remains the same, but drive is enhanced. So running the LCD-2 in low power mode with the m9XX already gets me all the volume I could ever need. But the bass performance is weak, and the midrange lacks focus. The whole thing is just soft and squishy. It's clearly underpowered. High power mode doesn't suddenly let me run at lower volume settings, but it does give a clear increase in drive. The LCD-2 regains its authority, with deep, clean low notes and a more insightful midrange. This same experience applies with the HiFiMAN HE-500 and Mr Speakers Alpha Dogs too. There's enough juice on tap in high power mode to get most planar magnetic headphones jumping, with the usual exception of Hifiman's HE-6. I also prefer high power mode with my Sennheiser HD650 and other high impedance models. Interestingly, I even prefer high power mode when driving the AKG/Massdrop exclusive K7XX. It's not the most demanding headphone out there but seems to really "wake up" in response to the extra power. It's handy to have both options available.

Overall the amp section is nearly identical to the DAC - both are clean, transparent, and highly resolving, yet not analytical or dry. The end result compares favorably to any number of more expensive devices I can think of. The original Benchmark DAC 1 for example, is more chalky and etched sounding to my ears, with a glare to the upper mids and a thin character that just don't enjoy these days. When it first launched back in the day, I admit to being taken by its seemingly extreme resolution, but I eventually began to hear it as artificial and obnoxious. Their DAC 2 is far superior to its predecessor and does manage to outclass the m9XX, as it certainly should for the price. The delta is not as large as you might think though. I also prefer the m9XX to the Mytek Stereo 192, which to my ears sounds dangerously close to the original Benchmark DAC 1. The Grace model has more life and soul, sounding better no matter what headphones or speakers I pair it with. The best comparison I can probably think of is the Anedio D2 which was selling for $1,249 last I checked, down from the original $1,470. The little m9XX gives a huge portion of the same ultra-transparent, open-window type of sound, at a far lower price and in a smaller package. I still find the D2 superior but spotting a difference requires some careful listening with excellent recordings - most people would find them very similar under normal circumstances. Those who know my opinion of the Anedio will understand just how big a compliment this comparison really is.

I never intended to turn this into such a long write up. I've got paid articles in progress for InnerFidelity and Part Time Audiophile which I really should be focusing on. But this little device gets me optimistic about what can be achieved through smart engineering and knowing what users are looking for - and what they aren't. Grace Design seems to have whittled down the technology and features of their far more expensive m920 in just the perfect way, while Massdrop allows it to be sold without a huge dealer markup. The initial drop is limited to 500 units and I suspect those will go very quickly - I'm hoping (though I have no verification at this time) that Massdrop will offer more drops in the future just as they have done with the K7XX. In any case, here I am rambling on and on about it instead of working on my "real" articles. Jude will have his say on the m9XX, as will several other experienced HeadFiers, so we'll see if my experience matches theirs. All I can say is that I'm thoroughly impressed by this thing, and think it might be a new benchmark (no pun intended) in terms of sonic results for the price.

Great review! Thanks 86, now the GAS is kicking in again and I just got it to stop!
Adam Kim
Adam Kim
I read your review on the Chord Hugo on Part Time Audiophile and m9XX here on Head Fi. Both excellent and detail review!! 
I know they are slight different animal one been battery operated and one not and not looking at the price difference, as far as the sound quality in terms of headphone+dac would you say that they are on par or the Hugo have an edge over m9xx or they are both equally good?
Of all the reviewer I think you could be the most qualified to answer this question.
And thank you for all the reviews you have wrote:wink: