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Massdrop x Airist Audio R-2R DAC: A Discrete Resistor Ladder DAC For $350

Discussion in 'Dedicated Source Components' started by jude, Jun 4, 2018.
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  1. One of the best DACs I have ever heard at any price is the totaldac d1-single-mk2. That totaldac happens to be a discrete R2R (discrete resistor ladder) DAC, and it is easily one of the two best DACs I've tried with the Sennheiser HE-1. The totaldac d1-single-mk2 is priced at €6400 (around USD$7800), and a significant part of the cost of the totaldac is in the resistors. If you buy only one of the totaldac's 0.01% VAR Bulk Metal Foil resistors from Vishay, it'll cost you around $15. There are 100 of them in the totaldac. If you're an enthusiast of (or interested in) R2R-type DACs -- especially the discrete resistor type -- then you know they do not come affordably.

    For a little primer about R2R DACs, here's how Massdrop introduces the concept:

    Why am I quoting Massdrop? Because Massdrop is bringing an R2R DAC to the market, and not surprisingly they are doing it affordably. To do this, Massdrop is working with Airist Audio, who had previously released a discrete R2R DAC model of their own. I'd heard Airist's DAC at CanJam Socal a couple of years ago, and it sounded impressive and promising.

    Massdrop and Airist Audio have developed a model called the Massdrop x Airist Audio R-2R DAC, and they're going to be dropping it very soon. It's housed in a chassis to match their new family of amps, and, like their amps, it's going to be affordable -- the most affordable discrete resistor ladder DAC I'm personally aware of at $350.00.

    In the Massdrop x Airist Audio R-2R DAC there are two independent 24-bit ladders with 48 resistors for each channel. Further, from Massdrop:

    wmqAg9BSQxOuGDadwNlz_airistinterior copy.jpg JB7clo6kQj2lUW9y9iir_AI7B7978 copy_new.jpg
    (Massdrop x Airist Audio R-2R DAC internal images above from Massdrop.com)

    To try to do this well at only $350 is a rather ambitious undertaking. They sent us a pre-production unit to listen to, and we've only had a short time with it. While I have not used it with the Sennheiser HE-1 (what an interesting pairing that would be), I have used the Massdrop x Airist Audio R-2R DAC with the iFi Pro iCan headphone amp (one of my reference dedicated headphone amps) to drive both the Sennheiser HD820 and the final D8000. Early impressions are that the Massdrop x Airist Audio R-2R DAC has a warmth and smoothness to its sound that is forgiving and free of edge. Is it the totaldac for $350? No, of course not. But in seeking to achieve the rich, warm, natural sound that many R2R DAC enthusiasts attribute to well-executed R2R DACs, my early impressions are that Massdrop and Airist's ambitions may be more realized than I'd have thought achievable with a discrete resistor ladder DAC for only $350.

    Massdrop x AIRIST R-2R DAC-7.jpg Massdrop x AIRIST R-2R DAC-1.jpg
    Massdrop x AIRIST R-2R DAC-4.jpg Massdrop x AIRIST R-2R DAC-5.jpg
    Massdrop x AIRIST R-2R DAC-2.jpg Massdrop x AIRIST R-2R DAC-3.jpg

    The dedication Massdrop has to affordably bringing some of the last things in hi-fi you'd expect to be made affordable is one of the reasons I find their approach to premium audio so refreshing. This Massdrop x Airist Audio R-2R DAC is just one of an increasing number of such examples from them.

    NOTE: Since we have a pre-production unit, I'll hold more detailed discussion for a production unit, as I believe they've already made improvements since this unit we have here was made. When we get the production version, I'll say more, and I'll also post a host of measurements of the production version Massdrop x Airist Audio R-2R DAC.

    Following is a link to Massdrop's drop page for the new DAC:

    Alcophone, jurumal, Mshenay and 4 others like this.
  2. project86 Contributor
    What do you look for in a DAC? Everyone has their own answer to that question. For some, name brand recognition is key - based either on respect for designer's reputation, or brand heritage, or simply pride of ownership. Others look for the latest and greatest DAC chip or proprietary FPGA scheme in lieu of off-the-shelf solutions. Some may want a tube-based output stage, and some look for non-oversampling designs (those last two groups often overlap). The remaining obvious aspects: feature set, aesthetics, and price, help narrow down the choices to a manageable handful.

    One choice that was all but replaced by newer technology, but is now enjoying something of a renaissance, is the R-2R DAC. This type of design can be done "on-chip" - the PCM63, the PCM1704, the AD1862, etc, all out of production at this point. Or, it can be built around a discrete resistor ladder network, which is definitely the trend right now. You'll find discrete R-2R designs at the heart of expensive models from MSB, TotalDAC, and Aqua HiFi, just to name a few, all with stratospheric price tags. But you can also find some excellent options from Metrum and Denafrips that aren't exactly low-budget, but remain within reach of many real-world users.

    One thing you rarely see is a discrete R-2R design in the sub-$500 category. The handful of R-2R DACs that do exist in that space tend use an on-chip design - not necessarily a bad thing, but it does give less freedom for the designer to truly make the device their own. The one exception I can think of is from Audio GD and it sounds pretty awful in my experience... so I try to forget it even exists (and I actually like Audio GD, in general). Seeing this hole in the market, Massdrop paired up with Airist Audio to bring us their own exclusive take on the discrete R-2R DAC, for a mere $349.


    I'm not going to waste time going into all the specifics, as the Massdrop x Airist Audio R-2R page does an excellent job giving us the scoop. But I do want to point out a few interesting aspects that stand out. Then, it's on to listening impressions.


    First up, Massdrop describes the heart of their design like so: "this sign-magnitude DAC has two independent 24-bit ladders with 48 resistors apiece per each of the two channels, which cancel out errors and distortion for purer processing." I'm told the resistors have a 0.05% tolerance which is better than Audio GD (0.1%) but not as good as Denafrips (which start at 0.01% get better as you move up the line). You'll find plenty of companies out there who don't mention that spec at all, so I'm pleased with what I see here.

    Tolerance isn't everything though. As Audio GD somewhat successfully argues, there are other clever ways to approach this issue. To that end, the Massdrop Airist R-2R (hereafter referred to as the RDAC) sports a CPLD with custom programming specific to this product. This works its magic to further improve the network accuracy. For those unfamiliar with the term, a CPLD is like a less complex FPGA, which is not designed to be upgradable in the field. While I love the fact that expensive DACs from PS Audio and Resonessence Labs can be upgraded year after year due to their FPGA cores, I can forgive a $349 product if it doesn't offer any improvements a couple years into ownership. Some of the more potent modern CPLD chips are nearly as powerful as their lower-tier FPGA counterparts, though don't expect Chord-level processing power here. Still, this all shows far more ambition than your standard off-the-shelf DAC chip sporting a slight variation of the reference design.


    The output stage is built around 5 opamps per channel. Each side gets a combination of three AD847s, one LT1128, and an OPA2134.

    Massdrop uses the modern XMOS XU208 USB controller and offers galvanic isolation across all three inputs (USB, Toslink, coaxial). The device can handle up to DSD128 via USB, or DSD64 (using DoP) on the SPDIF inputs. Clocking is done by low phase-noise units from NDK. Once inside the device, DSD signals are converted to PCM, as the ladder DAC can't actually process DSD. I'll discuss the ramifications of this soon enough.


    Worth noting: the USB connection is a microUSB rather than the standard full-size connection we normally see on desktop DACs. This has to do with size (the RDAC is not very tall) but also longevity... microUSB supposedly has a greater operation lifetime than its full-size counterparts, and USB C is not ubiquitous enough to be a good fit here. I thought this was weird and sort of annoying when I first encountered it. Now I'm used to it and don't think it's a big deal.

    The power supply is a 5V/3A wall-wart, augmented by voltage stabilization and regulation once the juice makes it inside the chassis. This, along with the somewhat minimal connectivity, is the most obvious sign of cost cutting. Old-school R-2R DACs that I've owned in the past almost universally sported massively overbuilt power supplies, so I was worried this would deter my enjoyment of the little RDAC. Again, I'll discuss this aspect momentarily.

    Notice I didn't mention build quality as being a sign of cost cutting. This device does not look like a budget product. The enclosure is low-key but well done, with the same interesting ventilation hole design up top as we find in the various Massdrop exclusive headphone amps. The LED indicators are deliberately soft (I hate bright LEDs that light up my room) which shows the care put into the design. Overall the device reminds me very much of the NuForce Home Reference series from a few years back - the most well done member of that family being their DAC100 which I believe was a roughly $1100 product. Not bad company to be in considering the price here. My only real complaint is that it doesn't quite have a satisfying heft to it - likely due to the power supply situation.


    Another quick note: I'm using a review loaner which isn't finalized in a few minor details. Specifically, the back panel will have some changes, such as relabeling the RCA jacks to say "output" rather than "input". Also you'll note the enclosure color doesn't perfectly mirror the "matching" Massdrop amp stacked on top. Apparently they changed the formula to make it less prone to fingerprint smudges this time around, but are still working on getting a better match. Don't be alarmed by that, and don't expect the final product to look identical to what you see in my pics... but it's close enough to give you the general idea.


    Now, onto the listening. My system consisted of the excellent Euphony PTS music server, powered by a Keces P8 linear PSU, and running Roon to stream music from a NAS in the other room (plus the occasional Tidal release). A simple CablePro Revelation power strip helped wrangle a maze of Cabledyne AC cables, while interconnects and digital cables from BetterCables made all the critical connections. Amplification came from the Massdrop Cavalli CTH, though I later swapped that out for a Rupert Neve RNHP, and eventually a Pass Labs HPA-1 for more critical listening. I also swapped in various USB decrapifiers in a quest to determine how well-sorted that input might be. Lastly, I added a Wyred4Sound PS-1 linear power supply to see what improvements could be had over the stock wall-wart. Headphones used were all over the place - Sennheiser HD650 and modded HD800, Fostex TH-X00, modded AKG K812, 64 Audio A18t, Audeze LCD-2 (pre-Fazor), Focal Elex, and Ultimate Ears UERM. That's a good mix of low and high impedance cans, with varying signatures and sensitivities.

    I wasn't quite sure what to expect. After all, my limited experience with Airist was not particularly impressive. I heard their one and only product, the Heron 5 headphone amp, when it first came out. For the $1999 price tag it carried at the time, I was not enthusiastic. It sounded decent, and external fit and finish were rather nice, but nothing stood out as being worth anywhere near what they were asking. I later heard the price was chopped in half which is a big step forward, though I still don't think I'd find the amp compelling in a sea of worthy competition.

    Connecting the Massdrop RDAC to my Euphony server via USB, it showed up in the system as a device called "Sandpiper". A quick Google search revealed that at one point Airist had what appeared to be a working prototype that they were willing to display at shows. I'm told that Massdrop worked with them on a number of design aspects centered around both improving the design and keeping the cost low. I don't know if Airist will ever come out with a version branded under their own name, but if so I'm told it will be something altogether different than the Massdrop RDAC. Note that production versions will display the correct "RDAC" info over USB rather than "Sandpiper".

    I first burned the RDAC in for about four days straight, mainly because I was busy with other stuff. To get a baseline sound, I started off with some old favorites in standard lossless 16-bit/44.1kHz resolution, played over USB from my Euphony server. Amplification was the Massdrop CTH (with the stock tube, which is hard to beat), and headphones were the trusty HD650.


    The resulting sound didn't really jump out at me - which I figure is a good thing at that stage. Whenever feel like I'm immediately floored by a massive holographic presentation, or insane detail, etc, that's usually a sign that something is blown out of proportion and will seem annoying after a short while. No, the RDAC was generally neutral, had very nice extension on both ends, and was overall unobjectionable in the best possible way.

    Upon further listening, I began forming the impression that the RDAC is, above all else, a very "natural" sounding DAC. From Meshuggah to Mendelsshon, timbre is convincing and lifelike, with impressive tonal weight that isn't overly accentuated. Soundstage is suitably spacious but, perhaps more importantly, surprisingly tangible. It's very rare that an affordable DAC manages to recreate that almost holographic, "reach out and touch the performers" feeling. Again, I've heard more height, depth, and certainly more width from other devices, but the RDAC captures a certain magic that goes beyond soundstage size. That said, with certain headphone and amp combinations, I could see the argument for finding it a bit restrictive - particularly if one is accustomed to the more artificially stretched presentation that seems popular in some circles. Not trying to disparage anyone but for me, accuracy and believability are more critical than sheer soundstage size alone. If you want more size without losing that natural feel... you'll have to move up to a significantly more expensive class of DAC.

    Switching gears, I swapped out the lovely sounding HD650 for the less forgiving HD800. In modified form it is less brutal than stock, but still very demanding on source quality. The RDAC did not let me down. Detail retrieval, like soundstage, is in one sense "adequate" but in another extraordinary considering the price. This thing is not a detail monster in the traditional way, where a tipped-up treble region creates artificial resolution. But neither is it dull sounding, or overly dark as some of the older R-2R designs could be. The RDAC comes off as prioritizing a natural sound versus stretching for more open, airy, and extended. It's not what I'd call dark, but it might take a bit of getting used to for some people. Then again, for some, it will immediately feel more "right" than most affordable DACs on the market.

    Treble is remarkably free from grain. Vocals sound particularly compelling, whether male or female. The raspy croon of Adam Turla (of Murder By Death) is placed on equal footing with the simplistic clarity of Chet Baker (yes, he sang from time to time, check it out when you get a chance) or the stunning Jacintha. All are presented with what I'd call an accurate, even-handed treatment, free from gimmicks or coloration. I normally expect this level of sonic truthfulness to come at a much higher cost. Would I like just a bit more air and extension? Perhaps, and if that's the goal there are ways to bring more of that out (which I'll discuss momentarily). But at $349 the performance is absolutely compelling. Again, we are talking about quality over quantity here, and I think the RDAC nails it in that regard.


    Switching to the $499 Rupert Neve RNHP headphone amp unlocked new levels of performance. As good as the CTH is, there seems to be more potential in the RDAC waiting to be set free. I noticed a more solid footing in terms of low end extension, which added a greater sense of rhythmic bounce to the presentation. I also found the lower midrange to be more fleshed out, while remaining very tightly controlled. The biggest improvement of all was the ability to more comfortably use my UERM and 64 Audio A18t, which don't play all that well with the CTH. The A18t in particular sounds amazing in this setup - bottomless lows, meaty mids, and delicate, flowing treble that seems perfectly balanced. This is absolutely a winning combo.

    The RNHP also confirmed what the CTH already hinted at - the RDAC has impressive dynamics and a black background, which makes bombastic classical (Stravinsky! Holst! Respighi!) a joy to play. It holds itself together beautifully when the music gets complex. Seriously, at this price, I can't think of anything that can touch the RDAC in these aspects. It's the type of thing which scales very well as the user upgrades ancillaries and headphones to tap its full potential.

    Lastly, swapping in the big Pass Labs HPA-1 brought another improvement, albeit a rather small one this time. Certainly not worth the extra expenditure over the little RNHP. That means the RDAC realistically tops out somewhere between the $499 Neve and the $3500 Pass - I didn't have time to continue searching for the best cost-to-performance dance partner, but I bet it's closer to the Neve (unless we add some upgrades to the RDAC....)


    When it comes to inputs, the USB lags slightly behind the coaxial. I didn't spend much time with the Toslink so I won't comment on it. Using coaxial out from my old but great Simaudio Moon Orbiter, I got even more convincing treble and slightly more accurate imaging. Standard USB is no slouch though - a lot of affordable DACs compromise in this area, by necessity, but the RDAC is perfectly presentable. Using a BMC PureUSB or a Wyred4Sound Recovery brings the USB back into parity with coax, or perhaps even gives it a slight lead - either way, the difference is small enough to be insignificant. I don't currently have a more affordable USB gizmo to mess with, but it's very possible something from Schiit or iFi would do the trick on the cheap.

    The plot thickened when I noticed that USB accepts sample rates up to 384kHz, while SPDIF tops out at 192kHz. I switched back to the Euphony server and set Roon to upsample everything to 384kHz. This brought out the best I had yet heard, even without a USB widget in play. Character didn't fundamentally change, but everything snapped into focus just a bit more - treble was more refined, imaging more precise, and the overall presentation even more weighty. Some DACs don't seem to care what you feed them but in this case, a diet of really-high-resolution PCM is just the ticket.

    DSD on the RDAC is interesting. Everything gets converted to PCM internally, but it still sounds quite good. I continue to believe the mastering on DSD releases is responsible for most of that format's benefit, and of course that's not something you lose even with an intermediate PCM conversion stage. I played around with having Roon bring everything up to DSD128, but that seemed to give a bit of edginess/crispiness to the treble - the first time I experienced that on the RDAC. It also did something weird to the midrange which I can't quite put my finger on... simultaneously too relaxed and too forward. I gave up analyzing it and went back to 384kHz upsampling and all became right with the world. Note: Native DSD64/DSD128 material sounds fine when played on its own. I just think the process of upsampling PCM to DSD in Roon, which then gets converted back to PCM internally, is not the best route to take. I'm undecided on whether downsampling native DSD to PCM in Roon rather than letting the RDAC do it internally makes any difference or not. Hopefully that all makes sense.

    Another upgrade I found was swapping the wall-wart for a Wyred4Sound PS-1 linear power supply. The PS-1 is a modular design, and you'll need to run the high current amp card to satisfy the 3A requirement of the RDAC. This really seals the deal in terms of treble refinement, dynamics, and the always desirable inky-black background. At this stage we are dealing with a $349 DAC supported by a $900 power supply - that's a bit silly, but it's the only thing I have right now with the proper 5V/3A specs. I suspect one could get most of the way there by spending less on another option, which would make more sense in this context.


    All I can tell you is this - the RDAC, powered by the Wyred PS-1, with a Wyred Recovery in the USB mix for good measure (also powered by the versatile PS-1), being fed 384kHz PCM via Roon upconversion, rivals many DACs I've heard south of ~$2,000. If one could achieve similar results by a more frugal PSU and USB decrapifier selection, then all the better.

    Is this ridiculous? Why not just start with a "better" DAC right from the start? Let's talk about compromises. Massdrop and Airist have developed an excellent platform. But their price target means they can only go so far. While they do give us power supply and USB solutions that work surprisingly well, they are likely held back by the $349 asking price. Those users who want to bring things up a notch (or several) are then free to spend more on upgrades in those areas, while everyone else still gets superb baseline performance. It makes total sense to me. I would happily recommend this solution over many "higher end" DACs which cost around the same price as the cumulative RDAC/PSU/USB widget, so they've done something right in the development of the core product.


    To wrap thing up: Massdrop's Airist R-2R DAC offers massive performance at a relatively low price. It's not ideal for those who demand sonic fireworks, with artificially large soundstage and boosted treble. If that's your idea of great sound, the RDAC will come off as boring and cramped. I happen to think the RDAC's presentation is the more "correct" version. It focuses on the fundamentals and makes beautiful, natural sound, much the same way my favorite vintage R-2R DACs did. But while many of those had an admittedly pleasing warmth, the RDAC is more neutral and even handed (though arguably still just a bit warmer than truly neutral). For offering a musically satisfying performance, with amazingly pure treble and accurate imaging, the Massdrop Airist R-2R DAC is a clear winner. Factor in the ability to upgrade it to an almost shockingly high level of performance, and you can see why it earns a very strong recommendation.
    Last edited: Jun 4, 2018
    bode, Seui, omniweltall and 9 others like this.
  3. Zachik
    I received the RDAC for evaluation on Saturday (2 days ago), and had very little time to play with it. I also had very little time to write-up more, but I would rather publish initial notes now, than wait for couple extra days :wink:

    Setup and caveats:
    I fed the RDAC through the fiber optic input, coming from my Gustard U12.
    The Coax output of the Gustard fed my Metrum Amethyst. That way both DACs were working in parallel.
    I have several desktop amps, but the only one with 2 RCA inputs is the Gilmore Lite Mk2. For that reason, I have used it for easy A/B testing.
    I chose (for no particular reason) my Sennheiser HD600 for the initial comparison.

    Initial notes:
    In a word: WOW!
    The comparison to the Amethyst is far from ideal for several reasons, but initial thought was - this DAC might be actually better. And at one third of the price!!
    Don't get me wrong, both DACs sound great, and listening to each was very enjoyable, but the ability to quickly switch, mid-song, helped emphasize the differences.
    The RDAC sounded like it had a lower noise floor, resulting in better dynamic range and details. The perceived added details were not taking away from the experience (I usually prefer warm and smooth sound signature).
    Again, I cannot emphasize enough that these notes are based on 2 hours of auditioning the RDAC and comparing it to my Amethyst.

    So why do I think the comparison is not quite fair?
    • Both DACs are fed by the Gustard U12, but one from Coax while the other from fiber optic cable.
    • The RCA cables used to connect both DACs to the amp are not identical.
    • There might be a difference in output voltage level between the 2 DACs. When switching mid-song, I believe the RDAC is louder, and it is a known fact that louder is interpreted by our brain as better.
    So, for the above reasons, the comparison could have (and will be) improved. Read on...

    What's next?
    • Swap Coax / fiber optic between 2 DACs and see if my observations "follow the cable swap" or "stay with the DAC".
    • Alternatively, get an RCA splitter like the "AudioQuest adapter - RCA male to two RCA female", and feed both DACs from same Coax output of the Gustard. Not sure if that splitter would degrade the signal quality going into the DACs or not (I do not have this splitter, yet)...
    • Get identical RCA cables to connect both DACs to the amp - eliminate RCA cable difference.
    • Get A/B switch so I could connect both DACs to other amps that have 1 RCA input. I have at my disposal: Massdrop LCX and CTH as well as Schiit Lyr3.
    • Measure DAC output voltage level - to see whether or not there is a difference between the 2 DACs.
    • Try other headphones - I have too many to list, but for starts: Mr Speakers AFC and EFO, HiFiMAN HEXv2, Campfire Audio Cascade.

    I will be happy to TRY and answer questions, as I am sure many people would have lots of questions!

    BIG thanks to @CEE TEE for giving me this opportunity to check out this really cool product. After owning the LCX and CTH, and now auditioning the RDAC - I cannot wait to see what else is coming from Massdrop. What a great time to be in this hobby!! :wink:

    June 7 update: see post #133 for additional impressions and notes.
    Last edited: Jun 7, 2018
  4. Torq
    About a year ago I was approached to provide some early feedback on a new multi-bit (discrete R-2R) DAC. It didn’t have a case. It didn’t have a projected price. It didn’t have a release date. And it didn’t have a name - simply being referred to as “RDAC”.

    First impressions were distinctly positive, even compared to some of the stalwarts in this space, to the point I was quite anxious both to learn what it might be sold for and to hear how the final iteration was going to perform. So, when about a month ago I was offered a unit with the final production electronics, properly cased, and ready to be subjected to a formal review, I jumped at it.

    Today the veil comes off and what is now officially called the “Massdrop x Airist Audio R-2R DAC” (or, “RDAC” for short) is public and being formally offered for sale, at $349.99, starting on June 6th:


    Major Features

    The interesting features of the RDAC are buried inside the unit - the exterior being an unassuming, but stylish matte-black housed in a chassis that stacks perfectly with the Massdrop x series Cavalli amplifiers:
    • Dual 24-bit discrete R-2R ladders, per channel, in sign-magnitude configuration.
    • Bit-level buffering/isolation on the ladder resistors.
    • Separate PCBs for the resistor ladders vs. I/O, conversion and other processing.
    • Internal power regulation and reference voltage stabilization.
    • Low phase-noise NDK clocks.
    • Custom decoding and filter implementations.
    • USB (galvanically isolated) and S/PDIF (COAX and TOSLink) inputs.
    • PCM native conversion up to 24 bit/384 kHz.
    • DSD support to DSD128 (via internal PCM conversion).
    Listening Notes

    Critical listening was done with the RDAC being driven via it’s USB input (after determining this was the best way to drive it in my system) via Audirvana+ and Roon. Source material was primarily 16/44.1 FLAC format CD rips, with some native high-resolution content and multi-rate DSD albums to test those capabilities.

    Primary listening was performed via an iFi Pro iCAN and a Woo Audio WA234 MONO Mk2, with some additional amplifiers included for pairing/system matching commentary. Headphones ranged from the HD650 to the Focal Utopia and Abyss AB-1266 Phi.

    Direct comparisons were performed in a hardware assisted blind(ish) fashion. Not strictly a fully blind comparison, but a lot closer than simple sighted listening.

    How Does it Sound?

    The TL;DR; here is simply that the RDAC sounds marvelous.

    The signature is one of general neutrality with a touch of sweetness to the mid-range and upper registers, and a distinctly “pristine” quality/clarity to the sound. Overall presentation is open with a good sense of air but is neither lacking, nor carrying too much, tonal weight/density. The RDAC’s rendering is fluid, articulate, nuanced and well balanced - capable of excellent top-end delicacy while simultaneously plumbing a tuneful, driving, bass-line and keeping vocals present and lucid.

    The strongest, and most enduring, comparison I can make for the Massdrop x Airist Audio R-2R DAC is that, at least from a signature perspective, it sounds like a Holo Audio Spring DAC and Soekris dac1541 got it on - and this was the result. It exhibits some of the sweetness that I found so beguiling with the Spring DAC combined with the distinctly “pristine” quality to the sound rendered by the dac1541.

    While the RDAC is not quite on the same level with all technicalities as those two units, it’s surprisingly close and the combination of their better sonic aspects results in a very compelling delivery with a broad variety of music.

    In More Detail

    Tone is lovely and pure, with just a hint of sweetness. I’d stop short of calling the presentation romantic or euphonic. There’s just enough “sugar” to keep the otherwise “pristine” or “super clear/resolving” delivery on the “musical side” of things vs. drifting off towards being “analytical” and is, for me, a more engaging listen because of it.

    Extended sustain on piano notes, from my own pieces, exhibit none of the strange tremolo or vibrato that I’ve found in some other discrete R-2R DACs that would be considered natural competitors to the RDAC. Here … the tone remains pure until the notes naturally ebb away.

    Timbre is natural and realistic. Instruments are easy to identify reliably, even in very complex orchestral works and when they’re separated by relatively minor familial differences, purely by how they sound (without resorting to locational cues). Individual oices, similarly, are easy to identify and localize, even when faced with multi-part close-harmonies.

    Transient performance is excellent, almost NOS-like in fact, with plucked strings, discordant brass and aggressive percussion all exhibiting surprisingly rapid and impactful attack/bite. Switching to electronic music and the impact and transient speed remains … play the first 60 seconds of “The Rat” (Infected Mushroom, “Army of Mushrooms”) and you’ll see what I mean. Or run something like “Along this Road: Kono Michi” (Ottmar Liebert, “One Guitar”) and the instant bite of the pluck and the reverberant decay against a deep, dark background.

    As I’ve said, there’s a hint of sweetness to the delivery of the Airist Audio R-2R DAC - and this is most in evidence in the mid-range. Lucid and transparent are also terms that come immediately to mind here. Vocals, particularly female, are present, well articulated, and unexaggerated. There’s no apparent emphasis or reticence. Just a natural, emotive, and evocative rendering.

    Something like “Ellis Island” (Mary Black, “Looking Back”) showcases this sweetness quite nicely. And being a semi-sweet piece in its own right helps to show when this sort of sound is taken too far … and with the RDAC it is not - it’s just where I like it.

    The upper registers are clean, smooth and properly extended, carrying some of that mid-range sweetness forward in a Goldilocks-like “Aaahh … just right” fashion. There’s a palpable sense of air and space and a very honest delivery. If there’s sibilance or harshness in the source material it’ll be reproduced faithfully, without ever exaggerating or exacerbating it. Cranking various pieces by “Heart” or “Julia Fordham” can be a bit of a wince-inducing torture test in this regard but were handled with aplomb by the RDAC.

    Playing a couple of “guilty pleasure” tracks here, specifically, “Buffalo Girls” and “Double Dutch” (Malcom McLaren, “Duck Rock”), through the RDAC shows that it is not going to gloss over faults or harshness in a recording (and you can hear well into the aggressive edits/mix of, say, some of Prince’s works) but it won’t make them worse either!

    At the opposite extreme, the bottom octaves, while perhaps not the absolute last-word in terms of low-end drive and slam, are only marginally behind the front-runners there and the RDAC certainly isn’t lacking in the bass-department. Playing some more bass-intensive tracks (Beyoncé’s “Partition” or Trentemøller’s “Chameleon”) shows no lack of weight, and excellent texture, speed and articulation. A run through Talvin Singh’s collection “Anokha: Sounds of the Asian Underground” is, similarly, fully satisfying.

    Stage is quite convincing. I only got to test this with headphones but even so the RDAC is capable of projecting a realistically wide stage, and the “sense” of space in a given venue is very well communicated - play something like “Mining for Gold” (Cowboy Junkies, “The Trinity Session”) and you’ll be subjected to a distinct sense of the simple, stark, natural environment the recording was made in.

    Layering and separation are typically strong points of R-2R implementations for me, and the Airist Audio R-2R DAC is no exception. Picking out individual instruments in a complex mix is easy as is tracking the melody while tapping your foot along to the baseline (which you’ll be hard pressed not to do).

    As mentioned initially, there’s a distinctly “pristine” aspect, and a strong impression of “clarity” and resolution/detail that’s evident even on first listening to the RDAC. There’s nothing artificial to this … the detail is real and notof the often-encountered “artificial hyper-detail” found in many D/S type converters. Brushes on cymbals or drum skins, decaying triangle strikes, and so on exhibit are resolved to a level that I’ve generally only found on rather more expensive units.

    Dynamics, both macro and micro, are addictive. “Sledgehammer” (Peter Gabriel) or the intro to “Twist in my Sobriety” (Tanita Tikaram), which are possibly opposite extremes, still both provide graphic illustrations of the ability of the RDAC to simultaneously handle large dynamics while maintaining deftness, subtely, and resolving power with micro-dynamics. Cohen’s typically gravelly delivery, perhaps exemplified in “You Want it Darker”, also serves as an excellent illustration of the Massdrop R-2R DAC’s ability to portray tiny, subtle, variations in volume modulation … which gives his voice a lot of its visceral emotion.

    All of this is set against a deep, dark, velvety-black backdrop. There’s no sense of veil here. Clarity is excellent and, again, “pristine”. Noise on the recording, be it from the tape, the environment (in acoustic recordings), and so on will be fully reproduced, but nothing is getting added to it. I think this is, as with a couple of other DACs I’ve listened to recently, a major factor in how pronouncedly some of the other positive traits are rendered.

    Technical Details

    Inputs and Supported Formats/Resolutions

    The RDAC offers three inputs - S/PDIF via COAX (RCA) and TOSlink, and USB via a micro USB socket. These are selectable, sequentially, via the “Input” button on the front of the unit.

    The USB input IS galvanically isolated, and the USB input doesrequire USB host power to function as a result. As is typical for isolated USB interfaces, USB power drives the source connection side, and power from the DAC itself drives the DAC side of the USB interface. This also means the unit will show up on your computer even if it has not been powered on.

    This isolation seems to be pretty effective as using the COAX or TOSlink inputs did not yield a useful, audible, difference in quality in my setup. Similarly, trying a variety of USB-to-USB “purifiers” and/or DDCs in the chain did not yield a conclusive improvement. So, while you may experience different results, depending on your precise chain, the USB input is the way to go with this unit in my opinion. Though the option for TOSlink is particularly nice if you want to pair this with a TV/AVR/game console or are having issues with ground loops.

    In general, though, to get the most out of the RDAC you’ll want to use the USB input. This will give you the broadest range of bit-rate and format support. Officially, USB will let you play PCM up to 24/384 kHz and double-rate DSD (DSD128). With S/PDIF and a native DSD stream you can get to DSD128 and 24/192 kHz for PCM. S/PDIF using DoP will limit you to DSD64 (single-rate).

    Interestingly, and I’ll stress that this is NOT something that is officially supported, nor guaranteed to work, I’ve been able to run the unit at 24/768 kHz and DSD256 (quad-rate) without any issues at all via USB.

    DSD Replay

    As mentioned, the Massdrop x Airist Audio R-2R DAC is natively a multi-bit PCM converter. It can accept native DSD inputas well as via DoP, but that DSD content will be converted to PCM before being fed to the actual DAC ladders.

    Absent completely discrete PCM and DSD conversion stages, all DACs must do some kind of conversion from one of these formats to the other. For example, the PS Audio DirectStream models convert everything internally to DSD before doing anything else, whereas units like the RDAC or the Soekris units convert DSD to PCM.

    What matters most, of course, is what the end result sounds like. Interestingly all of the positive traits I found in the unit are preserved with DSD source material – the same sense of clarity and “pristine” nature of the sound is fully in evidence, and the tone retains the hint of sweetness that I keep going on about.

    In practice, this turns out to mean that the relative positioning of this unit vs. the others I compared it to, remains almost identical regardless of whether you’re feeding the RDAC PCM or DSD. I will say that the low-end of the iFi Micro iDSD Black Label cleans up a little when fed with native DSD content, but at best that brings it on par on that oneaspect and overall, I still prefer the presentation from the Massdrop unit.

    No Snap, Crackle nor Pop!

    It is very common for DACs, even expensive ones, to exhibit nasty pops, clicks, and other noises when switching between DSD sample rates and between DSD and PCM content. So, it’s nice to find that the RDAC makes no utterances during such switches. The unit mutes momentarily during these changes. In general, this is transparent unless you’re skipping tracks. There was no intrusion into the replay of a normal playlist of mixed rate DSD and PCM files.

    Power & Power Supplies

    Power to the Massdrop x Airist Audio R-2R DAC is supplied via an external switching PSU rated for 3W @ 5v DC and uses a standard barrel connector. The external nature of the supply means that you can, if you are so inclined, substitute a suitably rated linear power supply instead. Note that all of the listening performed for the main part of this review was performed using the stock PSU.

    Out of curiosity, once the main listening was done, I did try a couple of different LPS units here:

    The Teddy Pardo “Teddy5/3” yielded a small reduction in the noise floor, a side effect of which meant very low-level detail was more easily discerned vs. the stock PSU. Though it’s worth bearing in mind that this particular PSU costs more than the RDAC itself, and the very minor change in performance probably isn’t worth it, nor is it likely to be routinely audible.

    The iFi Power, which is technically underrated for this application (2.5A instead of 3A), did notseem to offer any audibleimprovement at all. Though this is also an SMPS, just with more filtering and “active noise cancellation”.

    And my lab-grade supply - which gave a larger improvement than the Teddy Pardo unit, but at an even more ludicrous value proposition (several times the price of the RDAC).

    My recommendation is, worry about your headphone and amplifier first and when you eventually have nothing else to adjust, maybe add an LPS to the RDAC!

    Converter Technology

    The Massdrop x Airist Audio R-2R DAC is a 24-bit discrete R-2R (multi-bit, resistor/string ladder) sign-magnitude, oversampling, converter, using low phase-noise NDK clocks and a custom linear phase filter.

    That’s an impressive configuration for a DAC at this level, particularly the implementation of sign-magnitude conversion. This dramatically improves linearity vs. a simple ladder (as much as two orders of magnitude at -60 dB). In listening to other DACs using simple ladders vs. a sign-magnitude implementation it has been my consistent finding that a sign-magnitude approach yields clearly better results - even when compared to much more expensive units.

    Sign-magnitude converters use two separate ladders per channel to improve conversion linearity. With a single ladder, any non-linearity in the ladder winds up being relative to the full-scale signal. A simple R-2R ladder specified with 0.001% distortion actually has increasing distortion in inverse proportion to the signal level, reaching 1% by -60 dB. With a sign-magnitude implementation, as used in the RDAC, the specified distortion remains constant … so 0.01% at 0 dB stays 0.01% at -60 dB.

    Comparisons to Other DACS

    Schiit Modi MB (via USB) - $250

    For a long time, my go-to reference for an “entry level” DAC has been Schiit’s Modi MB. I still think that it is an excellent unit. The RDAC offers a sweeter presentation, better resolution and clarity and a darker background compared to the baby-Schiit. The difference is enough that I think the RDAC is the better buy, despite it’s $100 higher price-point - if you can swing it, you should in my opinion. The Modi MB does offer a slightly more impactful bottom end, but the difference isn’t huge and is likely affected to a much greater degree based on amplifier pairing.

    Schiit Modi MB (w/ Eitr) - $379

    Adding an Eitr in the replay chain ahead of the Modi MB and driving it via COAX brings things a bit closer together, however I would still place the RDAC ahead - particularly when it comes to clarity, resolution and top-end air/space.

    Chord Mojo - $549

    While the Mojo has a slightly warmer signature, the Massdrop unit exhibits better bass texture and weight/slam combined with a notably smoother higher treble rendering. Raw resolution is similar in the mid-range, but I prefer the tone of the RDAC. And the Arisit Audio DAC conveys a better sense of air and the general ambience of the venue with the acoustic recordings I tried.

    Bifrost MB (w/ USB Gen 5) - $599

    Next to Bifrost MB, the RDAC continues to deliver a blacker background, the sweeter presentation and there’s still a slight sense of better clarity out of the RDAC. But now resolution and micro-dynamics are largely on par and the Schiit DAC’s low-end drive is still slightly superior. Again, not a big difference, but absolute bass-heads might prefer the Schiit unit - depending on what amp they’re pairing with.

    iFi Audio Micro iDSD Black Label - $599

    Not a perfect comparison, as the Micro iDSD BL is not just a DAC and, as such, presents interesting variations in perceived value based on how it’s going to be used. AS a pure DAC, however, the smoothness of the Micro iDSD seemed to take a little of the edge off brass and discordant piano (that’s a negative, as far as I’m concerned) compared to the Massdrop DAC.

    The mid-range delivery between these two units is similar in terms of liquidity and resolution, though the “sweeter” delivery from the R-DAC works better for me without coming across as specifically romantic.

    Bass is rounder and fuller out of the iFi unit, but this came at the cost of a slight loss of texture into the mid-bass vs. the RDAC. I’d say quantityfavors the Micro iDSD and quality the RDAC.

    DENAFRIPS Ares - $650

    The Ares has slightly more weight in the bottom end than the RDAC, though perhaps not quite the Massdrop unit’s dexterity with a fast, multi-tracked bass line. Mid-range lacks the sweetness of the RDAC, which may or may not be a good thing for everyone. Transient response, particularly with plucked-strings and rapid percussion, favors the RDAC - as do both macro and micro-dynamics and raw resolution.

    Other Comparisons?

    At this point, it would be fair to say that I’m rather surprised at how high up the DAC-price-ladder the comparisons to the RDAC have already gone, without finding a unit that clearly outperformed it both technically and in terms of overall listening enjoyment.

    How high did I have to go to meet that target?

    It wasn’t until I got to the level of the RME ADI-2 DAC and the Soekris dac1421, both coming in at around $1,000, that I could say that I found something that was, across the board, better technically than the RDAC while being as enjoyable to listen to (I do still like the hint of “sweetness” from the RDAC, however). You should also note that those units give a slightly false sense of the level of price/performance on offer here as they include other features, including capable headphone outputs and, with the RME unit, a very rich EQ and DSP capability.


    The Massdrop x Airist Audio R-2R DAC is an excellent sounding DAC, with a slightly sweet tone, a distinctly “pristine” and clear delivery and offering very highvalue. In the month I’ve been listening to it, it has been unfailingly engaging and involving, while continuing to impress on technicalities.

    For the $349.99 asking price, the RDAC is an easy and enthusiastic recommendation.

    Compared to its primary competition, and some units that could reasonably, at least on a price basis, be considered one or two tiers above it, the RDAC offers both higher value and, for me, both better performance and a more enjoyable overall listen. As such I expect it’s going to prove to be somewhat disruptive in the sub-$800 DAC ($1,000 DAC/amp) market.

    Some of that has to be attributable to the Massdrop design and manufacturing approach, which clearly enables higher than expected performance at lower than typical cost.

    You can be sure that I’ll be joining the drop when it goes live on 6/6.
  5. PopZeus
    Intriguing... Very curious to hear listening impressions, especially when compared to other R2R DACs, such as those from Audio-gd. If only this also came with an HDMI input... I'd for sure consider putting one in my living room HT system.

    For those who don't have an R2R DAC yet, this is a no-brainer.
  6. CalvinW
  7. hans030390
    I'll skip the usual introductory stuff about the Massdrop x Airist Audio R-2R DAC (referred to as RDAC from here on out). You can read all that stuff on their product page.

    Though, I will drop a quick note that I dig the slimmer height profile. I really like what Massdrop has going on visually with these audio products. Moving on...

    I actually rather like the RDAC. I am pretty skeptical of discrete R-2R DACs based on past listening. Some have just been absolutely horrendous in my mind, whereas even the better ones always seemed to be missing something compared to a good chip-based DAC. The good ones seem to have this sort of noise removal effect that cleans up some of the microscopic goodies in your music.

    Color me surprised with the RDAC. It doesn't sound nasty, it doesn't sound boring, and it doesn't really sound like it's missing so much of that something. Or, if it is, I'm having a really hard time worrying about it given the positive aspects of the DAC and the relatively low price.

    If I had to quickly describe the RDAC's sound, it has a slightly warm, yet balanced, character and quick, but slightly soft, transients. Some might use descriptors like "analog," "musical," or "organic." It actually reminds me of the newer Metrum DACs with the latest modules. Think laid-back, but still engaged in its role. In fact, I'd go so far as to say it's like a lower priced Amethyst, but a little less forward in staging and more straddling that line between oversampling and non-oversampling.

    The RDAC has a nice, full, powerful low end with good extension. The midrange is liquid and free of congestion. The treble is on the softer side of things but has an effortless, clear quality to it, even if some of the overall details seem to not pop as much as they should. Unless you are opposed to this warmer tone and liquid, but very slightly soft timbre, it should just flow with ease in listening.

    It also has a nice sense of swing and micro-dynamics to it. It's nimble and grooves nicely even despite it's warmer, softer leanings. It's never boring, veiled, or smothering.

    The Schiit Modi Multibit (aka Mimby), in comparison, is more congested and grainy sounding overall. It struggles more with dense, complex material. It's not quite as powerful and extended in the low end. It sounds a bit more compressed when handling quick, staccato-like micro-dynamics. But the Mimby still shares similar macro-dynamic characteristics with the RDAC, maybe just slightly edging it out. Tough call.

    However, the Mimby does excel when it comes to portraying room acoustics, reverb, air, and an overall well-rounded, three-dimensional view of most individual elements in your music. Drums in particular seem more tangible and real on the Mimby, including the way the sound decays in the room.

    The RDAC, on the other hand, reminds me more of non-oversampling in how it excels with vocals, giving them a sense of being attached to a body with a chest cavity rather than simply being a recording through a mic. (Usually NOS makes almost all individual elements sound more 3D to me, albeit sometimes less focused too, but I don't think the RDAC fully captures that here quite as well as the Mimby. Like I said, the RDAC kind of straddles that OS and NOS line, so it's hard to stereotype its performance.)

    While the RDAC may initially seem to have better layering than the Mimby, I think that's because the RDAC is more laid-back sounding. The Mimby is more aggressive and forward. But if you listen closely, the Mimby bests the RDAC when you pull out live recordings or the like. You get a greater sense of 3D layering and room or venue acoustics. Not that the RDAC does poorly here, mind you (it's at least good), but that Schiit house filter does wonders to music in certain areas.

    Still, staging, layering, and some level of tangibility aside, the RDAC sounds very confident and sure of itself without a sense of showing off. The RDAC has that easy-going, natural, and musical swing sort of personality in spades.

    In terms of resolution and detail, I think the RDAC and Mimby are fairly close. Nothing really seems to be missing from the RDAC, though the presentation is certainly different due to the softer nature and lack of Schiit's own digital filter technology. I expect to see differing opinions on which is more resolving based on what one listens for. Even in my comparisons above, you see where they have different strengths and can imagine how a sense of resolution and detail might play out in one's mind.

    And that's what I think it boils down to: presentation. The RDAC to me doesn't seem like it's necessarily competing with the Mimby. They both have their pros and cons. When I circle back to thinking of the RDAC as more akin to the newer, excellent Metrum DACs, its purpose snaps into focus. I love those DACs, and the RDAC taps into that same feeling.

    At the $350 price point, the RDAC offers a lot for the money. Not everyone will love it, and that's fine. I think it offers something for those that lean more towards the non-oversampling sort of realm than it does those more fond of Schiit's latest multibit offerings. Or, even if you're just curious to try a different flavor, the price point presents little risk. Newcomers should rest easy knowing that, presentation differences aside, they're still getting a really great sounding DAC.

    So, yeah, I'm pretty enthusiastic about the RDAC and was caught off guard when asked to check it out last minute. And I was certainly skeptical. But I'm already pretty fond of it. It's well worth checking out so long as you know it may not cater to your particular tastes. For the type of sound it targets, it meets its goal and at a low price. Most DACs aiming for this sort of sound are either too expensive or are underwhelming regardless of price. This is an excellent addition to a relatively thin subset of the market.

    Source note: Only tested both DACs with the Soundaware D100 via SPDIF.
    Last edited: Jun 4, 2018
  8. heliosphann
    Hmmmmm. Color me intrigued.
  9. XERO1
    CEE TEE likes this.
  10. someyoungguy
    I’m confused by the pictures - there’s two L/R RCA jacks on the back, but they’re labeled input? These must be outputs, no? Are they just mislabeled?
  11. Torq
    They're outputs.

    The label will be corrected for the shipping units.
  12. XERO1
    My only gripe about it is that it has 2.5V of output. I really wish it had 2.0V instead, since that is the industry standard, and it would make directly comparing it to other DAC's (most of which have 2.0V outputs) a whole lot easier.

    Also, please make the holes for the RCA and COAX jacks bigger (or have the jacks stick out farther) on the production version. As they are now, most RCA connectors won't be able to fit properly.


    This DAC does look like it's going to be amazing, though. A big thanks to Massdrop and Airist for making this happen! :L3000:
    Last edited: Jun 4, 2018
  13. Zachik
    Totally agree - read my initial impressions (post #3) which also mentions that during A/B test RDAC sounds louder than the other DAC (Metrum Amethyst).
    I did find attenuators on Amazon (see: https://www.amazon.com/Harrison-Labs-Line-Level-Attenuator/dp/B0006N41AG/) - they come in 3dB, 6dB and 12dB versions, but I do not know which would be the right one (if any) to lower output from 2.5V to 2.0V...

    Anyone got any suggestion on how to lower the output voltage (if only temporarily for comparison sake) to 2.0V ?
  14. maxh22
    @Torq How does it compare to Hugo 2?
  15. project86 Contributor
    Good point, it does make comparisons more tricky. You can always attenuate a bit using a quality software solution (Roon etc), though that still doesn't help as far as knowing exactly when you've hit 2V.

    As for the jacks, I just double checked, and the RCA outputs on the RDAC are identical to those on the RNHP. The RDAC RCA jacks do stick out noticeably more than the Massdrop CTH if that's any help. The RDAC coax input could stand to stick out more though. It look more like the CTH RCA jacks. Still, no problems on my end using a variety of interconnects just fine.
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