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Desktop Amps item created by TheOneInYellow, Jan 7, 2012
Pros - Sublime Transparent Sound, Price, Build Quality, Adaptability.
Cons - Maybe could have used the source input & PSU inputs at back
1st things 1st I guess ;
I tip my hat to the Guy who Designed the O2 & to JDS Labs also for making it ready built.
Now I don't know the Guy who came up with this O2 Headphone Amp but if I did I would certainly shake his hand.
I don't say this lightly but here it is then ;
This little Headphone AMP is quite simply put the best sounding Headphone AMP I have ever heard, PERIOD !
You add in the fact that I imported it into the UK direct ready built by JDS Labs for just under £100 including a UK PSU for recharging & I guess that possibly makes this little gem then truly the best value for money Hi-Fi component I own including any full Size Hi-Fi components in my Linn/ Musical Fidelity main Rig.
I normally use this paired with my now favourite cans the Shure SE 535 Ltd red's & all I can say is that it's like I'm listening to my big Hi-Fi System through it's Linn speakers & not through a Headphone AMP/ Cans combo
I cannot stress the clarity/ transparency of this little AMP enough, it's just a breath of fresh air in an otherwise "Snakeoil" & Overpriced, Overhyped & quite frankly mostly Junk Headphone Market. If you buy into the "Oh it has to be a brand name for it to sound good & thus cost a plenty style of thinking" then you'll probably never even get to try this little gem as you'll be too busy handing over £1,000 for your branded heap of junk headphone amp that you only bought because you "Like that brand & somehow think that they'll always produce greatness".
I have heard a few shall we say just Higher Priced Headphone AMPS & I won't mention any names as I don't want to even give their brand names any attention whatsoever when I'm talking about the O2 Headphone AMP instead so we'll leave at this statement then regards how it measures up to other Headphone AMPs costing even £1,000+/-'ish range ;
IMHO it wipes the floor with the lot of them !
Sure some maybe have a Remote Control or some maybe claim their made of Diamonddilliam but very very few will even publish their "Data/ Specs/ Info" on their real world performance so read into that what you will.
So performance wise it's hard to beat this little gem.
On practicality etc...
Sure you could use this portable but you'd need big pockets or perhaps even a little bag or backpack if you really wanted to venture into the urban jungle with it.
I personally don't go portable with it since I own a Clorfly C4 Pro & that is an excellent player that needs no amplifier at all as it'll go loud enough to make you deaf
I use my O2 for tapping into my Living room's Linn/ Musical Fidelity Hi-Fi's Streamer for its Flacs/ Wavs & Inet radio rarely
I use it also for tapping into my bedroom System again a Linn/ Musical Fidelity's Streaming source or again rarely Inet radio.
I guess I should add that I use a Custom made Phono to Mini-Jack Solid Silver Litz Cable a friend made for me especially for this purpose (It's about 3.5Metres Long), I would recommend if your the type who looks for weak links in their Hi-Fi chains then perhaps consider your cable & indeed your cable for your Cans too which is again in my case a Silver Custom job.
I find silver to be very transparent compaired to some of the more expensive options out there.
Back to the O2 ;
I tried it with loads of cans & was never disappointed once, as you pretty much get what you throw into the O2, you give it some trance in 1 side then some nice tight bass comes out the other etc... Didn't find any type of music that it didn't do justice with at all.
I'll say this though, if you throw into it a 128kbps MP3 then that's what you'll get at the other end, so in a nutshell feed it well & you'll be rewarded.
Only downside I see to this is that I do think maybe a little redesign so as the inputs are at the back would be nice & perhaps some1 has now done this, but I prefer sound quality over a small flaw in design any day
So to some up then ;
AMAZING VALUE FOR MONEY !!!
Laughs at the bigger boys & their £500+ AMP's IMHO
Buy 1 as you simply won't be disappointed I promise
1 last thing, please no dumb replies with statements of but this £1,000 branded 1 I have is way better as This is just an opinion so don't throw a hissy fit because I think this little gem is great Mkay ?
Pros - Very accurately reproduces the source signal; I guess it could help if the source's headphone jack isn't strong enough
Cons - Could use more power
The objective facts
Background: I listen to music on a higher-end (purchased for $800) Asus laptop, or my Galaxy Note 2 smartphone. With my SRH940s, the phone sounds better in terms of sound signature, but with my Sennheiser HD800s, the laptop sounds better for some reason. But they're both very close. All of these experiments were done listening to music on Spotify 320kbps; that's how I listen to headphones 99% of the time so that's the only way to test for my purposes.
How I tested this: I connected the O2 amp, with low gain, to my laptop's output jack. I set the volume of the O2 amp to its highest level (in other words, I controlled the volume of the music from my laptop's volume meter). The playback was set at 24bit / 192 khz (basic windows audio lets you pick this option). I plugged the HD800 into the amplifier.
The first thing I noticed was that this setup didn't cause the HD800 to be that much louder than it was when I simply plugged it directly into the laptop. In other words, with the O2 amp's volume set at max, and my laptop volume set at 25%, the headphones had close to the same volume as when I plugged the HD800 directly into my laptop and set the volume to 25%. So my laptop has as much power as this thing. Then I turned up the volume to the maximum and used a decibel meter to see how loud the two could make the headphones, and again, very similar. I repeated the above with the phone and got more or less similar results.
Next I cycled through a few songs that are very well recorded, to see if they sound better on one vs. the other. I listened once, twice, three times, again, again, focusing on very specific parts of the song, often playing 10 second portions of a song and repeatedly alternating between the two sources. I could find nothing. I would often focus on one tiny detail in a song, to see if the O2 and computer produce it the same, and they could. When the O2 was driving the phone, it had the phone's less desirable sound signature, and when it was driving the laptop, it had the laptop's sound signature, but the O2 didn't change the sound at all. I thought an amp was supposed to improve the sound of my "power hungry" HD800, but this did nothing. However, commenters say that this is exactly how it's supposed to work. In other words, it's not supposed to change the sound at all. So I guess I can't rate it poorly for doing what it's supposed to do.
Conclusion: If you have a severely underpowered source and need power, this will deliver it. But it could do more in this respect. It's not underpowered like some of those pathetic portable amps you see out there. But in my opinion, a $130 desktop headphone amp should provide boundless power, as much as you could ever want. When you buy a desktop amp, you should no longer be concerned about not having enough power. You should be concerned about keeping the volume low so as not to blow out your ears. To provide technical stats, on its website, it states that the O2 can only deliver a maximum of 88mW at 600 ohms. Well what if you're trying to drive a T1 or another 600 ohm headphone? Is 0.09 of a watt enough? Again, it has power, but you might not need the little bit of extra power this provides, and you might be fine sticking with your laptop or phone's amplifier. In light of the fact that it costs $130 and sits on your desktop, but doesn't have huge bountiful power, I'll subtract 2 stars. I'm just not sure why you would buy this if you want a desktop amp.
Pros - Neutrality, Definition, Cleanliness (Black Background), Articulation, Speed (PRAT factor), Imaging, Transparency, Power, Value (Price/Performance)
Cons - If you prefer a certain sound signature from an amp, it has no obvious character of its own, therefore it depends on our source and headphone choice
I have always loved the Grado RA1 which uses the high output NJM4556 op amp. It was one of my very first introduction to the world of headphone amping, and for years it was the mainstay of my main listening rig, both desktop and portable. The JDS O2 amplifier is using similar op amp(s) for its output stage ( and doubles it!), thus I found this JDS Labs Objective2 amp to be easily lovable right from the first listen. It does bear a resemblance in sound to the RA1, but it has more definition, cleaner sound, and more power as well.
I had owned a lot of affordable amps: the various CMoys ( I have owned most major CMoy version:JDS, Zigis, Penguin Coffee Amp), 3 Channel PIMETA, Schiit Magni, RSA Shadow, XCan V2, GSP Slee Solo mk2, RA1, PA2V2, Creek OBH11 amp, and Fiio E12, but the time had come to downsize the number of my amps. I sold the others (I need the money to get an iPhone 5S, which is unsubsidized in my country's market) and kept the O2 as my one and only one amp after months of evaluating them side by side. It came down to these three: Schiit Magni, RSA Shadow, and JDS Labs Objective2, and then I picked the O2 out of those three. I haven't regretted my decision ever since; I very much enjoy listening to Smooth Jazzes, the likes of Lee Ritenour, Earl Klugh, Fourplay, David Benoit, Dave Grusin, Incognito, etc. with this amplifier. It's paired with the following: AKG K702, Audio Technica ATH CKS1000, Philips Fidelio S2, or VSonic GR07 mk2, and also with the ODAC, Rockboxed Sansa ClipZip or the iPod with DIY iMod as the source. I love how the amp effortlessly disappear allowing me to enjoy just the music.
Pros - Excellent sound quality, great price/performance ratio, battery and/or AC powered, adjustable gain options, no background hiss, packs plenty of power
Cons - Everything is on the front-panel, low-volume channel imbalance, too bulky to be used as a portable amp, finicky with TRRS jacks
Without referring to "He-Who-Must-Not-Be-Named's" (A.K.A. NwAvGuy) blog, and speaking from my own listening experiences, I really do think the Objective 2 is a great headphone amplifier. No, I don't think this is the amp to end all amps, but it's a dang good one and it only cost me $156 USD (which includes the Triad brand WAU12-200 AC adaptor). In fact, it can be found even cheaper nowadays from the same vendor, JDS Labs, for $140 (including the same adaptor).
What's in the Package?
JDS Labs Objective 2 headphone amplifier, wrapped in an anti-static bag
2 removable, rechargeable Tenergy 9 V nickel-metal hydride (Ni-MH) batteries (already installed in the O2)
4 adhesive clear-rubber feet
3-foot long Monoprice mini-USB to USB cable, with gold-plated connectors and a ferrite bead
JDS Labs business card/contact information
2-year warranty free of part/manufacturing defects
Triad WAU12-200 AC adaptor (if purchased)
There are also 3 things you can get customised when your order your O2; all you need to do is fill out the "order notes" section before you make your purchase:
Specify if you want a free custom laser etching (source: http://www.head-fi.org/t/643435/review-jds-labs-o2-black-edition-o2-odac-discussion/345#post_9560679)
Specify if you want an alternative gain option (you can do this yourself by-hand, or JDS Labs can do it for you)
If you do it by hand, you can follow this guide to get 2.5x/1.0x gains, or 1.0x/6.5x: http://www.jdslabs.com/pdf/O2_LowGain.pdf
You should contact JDS Labs before ordering the O2, but it's possible to purchase a larger O2 unit with a 6.3 mm output instead of the standard 3.5 mm one and/or have the option to add RCA inputs for a $10 fee (source: https://www.facebook.com/photo.php?fbid=622772244410229&set=a.347705048583618.85653.213109922043132&type=1&relevant_count=1)
This isn't part of the special "order notes" customisation options, but you have the option to order the O2 with either black or silver endplates. I would recommend the black ones if you don't like to see scratches on your devices since the silver one that I have tends to easily show scratches (see photo below).
This is the only place where I have major complaints about the O2.
Everything is on the front-panel, and the front-panel only
12 VAC AC adaptor plug
3.5 mm output
Red LED power indicator
3.5 mm output
Yeah...there's a lot stuff going-on on the front-panel, and the cable management is a mess.
Adding to the mess of stuff on the front-panel, the amp itself is too big (for me) to be considered a portable amplifier. Perhaps for those people who carry around a "portable" bomb rig that is 6-inches thick with 4 different components and paired with a 10 pound open-back Audeze LCD-2 headphone with $500 platinum-coated silver interconnect cables (slight exaggeration here), this amp is trivial in size; but I am not one of those people and I prefer to have a tidy, pocketable portable rig instead.
Kidding aside, the other thing that bothers me with the O2 is the channel imbalance encountered at low volume-levels with the potentiometer. When past the channel imbalance region (~8:30 o'clock position on the potentiometer), the output is kind of loud even with 1.0x gain, especially with sensitive headphones. Because of this, I don't really recommend the O2 for such headphones unless you have a custom gain of less than 1.0, or you use an impedance adaptor.
As a small note, at least with the V-MODA Crossfade M-100's cables, my O2 doesn't seem to like TRRS jacks too much. If I plug it in all the way, I get a mono-like sound coming out of the O2. Pulling out the jack slightly seems to remedy this issue and all is good.
All things considered, the layout of the O2's front-panel is messy and the potentiometer's channel imbalance can be a bit of annoyance for some headphones.
The O2 outside of its case:
From switching between different amps, headphones, and sources I have at hand, the O2 has a very clean-sounding signature as a whole.
Bass extension is good with decent texture
Midrange is a bit laid back in presentation, but not lacking in detail
Treble is well-extended with no roll-off from what I can detect
Soundstage is pretty spacious, having both good width and depth
Related, but not necessarily correlated to the soundstage, imaging is also very good and I can easily imagine where instruments are in my head
Instrument separation is excellent; instruments are well-defined and never muddled together
Related, but not necessarily correlated to the instrument separation, instruments have very good detail and nothing sounds muffled
There is no background hiss from what I can hear with 1.0x and 2.5x gain options at reasonable volume levels
Q: Is this what neutral sounds like?
A: I have no idea. I'm not a musician, nor do I play any instruments, so I can't say if it sounds coloured or not.
Q: Is this what a "wire with gain" sounds like?
A: Maybe. This relates to the previous question.
Q: Is this what "boring" or "sterile" sounds like, as some have suggested?
A: Not in my book. Different genres of music of all different kinds of mastering sound fine with me. I have yet to encounter a track and exclaim: "wow this amp is so boring! my music sounds so dull and lifeless!" All I can say is that music in general sounds spacious, well-defined, and clear. Though "involvement" in music is purely subjective, I never find myself being uninvolved in my music unless I'm listening to music as background noise.
Q: Will it power X headphone adequately?
A: Yeah most likely. I really enjoyed the LCD-2 with the O2 over other amps I've heard, even though the LCD-2 isn't my favourite headphone of choice. From a pure synergy perspective, I didn't like the HE-500 with the O2 as it had a pretty tizzy treble that made rock tracks not enjoyable for me to listen to. That might be due to the HE-500 itself though, not the O2.
Q: Does it sound bright?
A: Not at all. I don't know where people got that idea from.
Comparing different headphones with the O2 and comparing the O2 to different amps, the O2 is definitely not bright to me. It's definitely not dark either for that matter. Maybe with an HD800 or K 701 they sound bright, but the those headphones are bright by nature, so it's not the O2 sounding bright.
All in all, if you can get past the messy front-panel and the channel imbalance at low volume-levels, then I truly think the Objective 2 is a terrific-sounding amp. I like its sound more than other amps I've tried, both desktop and portable amps, and everything just sounds so dang clear and clean to me. As such, the O2 is my current reference amplifier. For $140 USD, I think the O2 is a no-brainer if you're looking for a clean-sounding amplifier and you don't want to spend OVER 9000!!!!! (read: a lot of) dollars on an amp. You might not like the sound of some headphones out of it, but I think it's due to the headphones themselves and not necessarily the O2.
Thank you for taking the time to read or glance over my review! I hope this review helps you in some way or another and if you have any questions, feel free to leave a comment below.
Pros - Transparent (duh), Not bright/thin/cold and requires no specific type of headphone
Cons - don't like the inputs on the front
Just a few impressions since nobody really reads these:
All my headphones work well with it. Everything sounds just like it should. Garbage tracks actually still sound like garbage.
Very revealing (yes, I know) and if my recording sounds tinny/harsh/thin it will sound like that (unless I'm using the HD-650) without any change
Doesn't sound bright (if it does, it's the recording or headphone) and doesn't require a specific type of headphone for good "synergy" (IMO so far).
Doesn't sound cold/thin etc. It's warm (sounding) if the recording or headphone is. Some recordings sound like they have all the warmth sucked out.
Sounds crystal clear really. It actually might sound maybe a tad cleaner than my Micro Amp + Astrodyne. Barely audible, but I noticed it.
Didn't notice any "larger soundstage" nonsense, but I did get an impression of a little more detail. I think i'm just fooled really.
I would say it sounds perhaps 97% identical to my Headroom Micro Amp + Astrodyne. Impressive! The Micro might have a tad more body to the sound, but barely audible. It's not warm!
I can't say this enough, but the O2 sounds closer to the Micro Amp than the Schiit Magni (IMO).
I don't like the layout and would gladly pay $50 more for a design with inputs in the back. I'll live.
If you like a just a slight touch of warmth on your amp I would suggest instead the Fiio E9 or get an E17 as a DAC.
I don't really know what else to say. Nothing really WOWs me except for how crystal clear it sounds (with the right music) and how close it is to my favorite Micro Amp.
Tested with Schiit Modi, E17 (DAC) and HD-650, K400, Q701 (+Annie pads), Koss Pro DJ 100, HD-598.
The coolest thing to me with this is the massive variation in how each recording sounds sometimes. At times it feels as if it's like going from an HD-650 to an AD700. This is with the Q701!
So far I like this more than the Fiio E9, Asgard1 and Magni, but it's comparable to the Micro Amp in sound. Is it better? Not sure.
Doesn't get hot. I just checked. Had it on the past 4 hours.
Might sound .000005% better with the ODAC compared to the Modi. Modi and ODAC sound nearly identical to ME.
Sounds transparent. No, really. I bet you didn't know that! I've heard it with my own ears and agree.
Seems like with the Q701 it has a very very very slight hint of treble brightness. Barely audible, but it's still great with bright headphones and won't make them worse really. I've read that upgrading to a different power supply might make the treble smoother. Doubt it, but maybe!
Guns in Fallout 3 are noticeably more ear piercing than usual, but not too bad.
Pros - Noticeable improvement in some cases, very little improvement in other cases
Cons - Everything is on front panel
So, this amp makes the signal just a bit cleaner. It was pretty noticeable on my Q701s, noticeable for general clarity, separation, esp cymbals got a bit clearer. For my HD 558 (w/ foam mod), slightly noticeable, but not that much. For my closed-back headphones->very minuscule, you might notice if you listen really hard. When I bought this, I just needed power for my Q701s so I was surprised the quality actually improved, thus I might have exaggerated my initial impressions a tiny bit. Overall the difference minor even for the Q701, but still pretty noticeable. It's not OH WOW I CAN'T BELIEVE THIS, IT'S LIKE DAY AND NIGHT kind of difference.
I bought this amp for my Q701s (Which I won't receive until Friday). When it came I took it out just to make sure it works (All my current headphones are low impedance and don't require an amp). I hooked it up with probably one of the worst possible sources you can imagine: a Nintendo DS (I was in the middle of playing a DS game when it arrived). Of course there was volume, but I also almost immediately noticed that the soundstage got bigger and the instrument separation became better. This was on my AD700s. I thought to myself it must be me imagining things. Just to make sure I switched back to directly plugging into the DS and the DS->Objective2->Ad700 setup. There really was an improvement, not just volume, I adjusted the knob so that the volumes were the same. The improvement is definitely real and doesn't require careful listening to notice, it was almost immediately noticeable. Needless to say, I am impressed as I have always been skeptical of headphone amps, but this one made me believe all the hype.
Pros - Everything?
Cons - Need bigger am for HE-6?
Linear, low output impedance and never noisy without a "signature". If you want to listen to your headphones and not your voiced headphone amps I highly recommend this.
Pros - Does its Job and Does it Well
Cons - Pricey? Even for what you get . . .
Lets see, a battery powered Amp that runs for hours on hours with a charge, or a desktop Amp that can throw almost a watt out and run forever?
I don't know - its sort of both. It is too big to be taken anywhere, but definitely small enough to travel if you want it to. I ordered mine with a black face plate which I think is a little cooler looking.
There appears to be some "mythology" surrounding this amp, some claim it "ruins" their sound quality while others think its awesome. I think its an amp - that is, it takes a signal, amplifies it, and otherwise has no real impact on what you hear. It has no real noise I can detect (except at max gain of 6.5X with nothing playing at max volume, which is possibly my source, not the amp). Those who adore vacuum tubes might hate this discrete amp, but I hate replacing tubes every 9,000 hours, and like the idea that this thing should run forever
As far as amps go, the sound quality has been awesome, convincingly "clean", and does not seem to distort or struggle even when being pushed hard. You would have to spend at least another $50-100 bucks or so to get to the next level of power (about 1 full watt) with similar features and quality.
Mine came with small stick-on rubber feet, and a blocky 12 V DAC adapter. Having all jacks in the front is not a HUGE deal, but function is definitely following form in this case. Clutter could be reduced if the power and input jacks were in the rear, but you'd have to do these mods yourself. On that front, it would be nice to have digital/RCA/USB inputs as this unit probably isn't going anywhere. Whole unit has a nice solid feel, volume knob is solid feeling. Only gain and power switch come across as a little "cheap". I ordered stock 2.5X gain and 6.5X gain switch - which is about right for my HE-400s. For a more efficient headphone, as you can choose gain level, I would recommend 1X gain and perhaps 2.5-4X for less efficient cans. If you listen to many High Dynamic Range recordings (like DVD movies, for example), you may want that high gain (6.5x) switch - it can help reach the right volume levels with certain headphones. But, in general, the gain settings are not 'volume' buttons consider your main sources.
JDS Labs shipped extremely fast, answered my questions, and will "customize" the unit by shipping it with gain settings and color of your choosing. You can choose your own VAC adapter, or just buy theirs, as I did.
Prodigous power from a small unit - I estimate about 700 mWs @ 50 ohms while plugged in. Otherwise, about 500 mWs reliably from about 32-100 Ohms plugged in, and about 500-400 mWs on battery. Far more power than needed for most headphones. Very low impedance output should be a great match for a very wide range of headphones. This thing specs better than amps several times its price.
That said, it also costs almost as much as very good component amps for cars (that provide 10x the power). It costs as much as some very good headphones. In the world of high-end headphones, it is a fabulous value. But I would probably skip it if you get enough volume from current sources. The HE-400 provides a fairly good threshold perhaps (rated 92dB efficiency). Any phone with efficiency ratings in the 95 dB or greater range probably doesn't want this much power. But if your phones are high impedance and you struggle getting good output from a computer, phone, etc, I am sure the O2 will rock your world.
Pros - Good sound, low price, portable
Cons - I don't like the layout
Okay... I believe the O2+ODAC combo is a good product for the price.
Yeah, that does sound like a cop out, doesn't it? Alright, I'll try again.
With headphones that this unit will normally be paired with; HD650, Q701, HE300, FA-003, etc. (solid mid-fi cans), I think it does quite well. To me it stumbles where most SS mid-fi amps stumble, it's a little on the bright side of neutral and highs are a bit etched. Also, mids do seem slightly congested and bass could be tighter. Also, mine has a slightly scratchy volume pot (not a huge deal, probably just needs a shot of DeoxIT). I don't think it drives my T1s very well, same goes for the TH900. Those foibles I mentioned before seem to get magnified. The HE-6? Fugetaboutit.
"Oh, he hates it", no I don't. It isn't some Class A monster, and my Onkyo P-3000R ($1700 MSRP) does knock its lights out, but it's $300 and has batteries for cripes' sake. Personally, I feel the DAC is quite good, though I wish it had some type of S/PDIF connection, and as a package it punches above its weight class. IMO, it isn't David knocking out Goliath, it's a Golf GTI out handling the mid-range pony cars. Overall a good value.
Pros - Transportable, sound great with LCD2s, cheap
Cons - a little big for your pocket
This is a perfect transportable amp with size similar to Hifiman HM801.
When couple with a Sansa Clip, the sound quality beats my previous HM801 w/o external amp.
It drives all of my headphones very well, including LCD-2s, DT880s/600ohm and Westone ES3Xs (IEMs).
Overall sound quality is easily at the same level of full size amps costing around $300-500 USD. It does not seem to add any flavor to music, more like wire with gain. Very transparent.
Some of my previous impressions can be found here: