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Taken for item page: "The Objective2 (O2) is an open source headphone amplifier designed by...

JDS Labs Assembled Objective2 Headphone Amplifier

  • Taken for item page:

    "The Objective2 (O2) is an open source headphone amplifier designed by NwAvGuy, with emphasis on benchmark performance and low cost. This item includes a fully assembled and hand tested O2 amplifier, ready for use. You will only need an AC adapter.

Recent Reviews

  1. PedroVazquez53
    Perfect in almost every consideration
    Written by PedroVazquez53
    Published Aug 22, 2017
    Pros - Has power, it is almost without distortion (if you can hear any), it's attractive and compact, and the DAC is clear.
    Cons - Only found this: the gain of the O2 is not so high, ask JDLabs that they send your amplifier with higher gain. Some high impedance phones lack punch. But this is no hardship. Their other models have more gain.
    I came upon the article by the navguy and almost instantly ordered a kit. I was amazed at the sound of the kit, so later I ordered one O2+dac. I am an electronic technician, so I have assembled and purchased many headphone amplifiers and after testing many I am convinced that this O2, the concept of Navguy, is one of the best amplifiers in the market. You can also try the Cmoybb to hear a good bass and the clear sound will amaze you. I recommend these products to everyone. Period.
  2. SoundApprentice
    A budget-audiophile's delight
    Written by SoundApprentice
    Published Feb 20, 2017
    Pros - Price-to-performance, transparency, custom options
    Cons - A bit "boring" by nature
    Meant to be married to the OL DAC, the O2 headphone amp matches it in shape, size and simplicity. What’s neat about the O2 is that JDS Labs allows for some simple customizations—you can choose the headphone jack size (3.5mm or ¼”), input type (RCA or 3.5mm), gain levels, and power jack location (front or rear panel), and whether to have it with or without a built-in DAC and lithium batteries for portable use. I went with a rear-mounted power jack and RCA input, so my front panel is nice and simple with just the power button, headphone jack, volume knob, gain button and a red LED power indicator (why red instead of green to match the OL DAC? I don’t know, but it kind of bothers my OCD).

    So how’s the little black box sound? Well, it follows the open source amplifier design from the aforementioned NwAvGuy. In other words, it targets benchmark performance at a budget cost ($129). So, much like the OL DAC, the O2 amp aims for transparency. Or maybe a better way to put it is simplicity. 

    For those of you that are used to colored amps, there’s nothing romantic about the O2. In fact, it’s likely to come off as a bit dry, a bit sterile, a bit, well, boring, just like the OL DAC. That is, unless your DAC is colored in another way. After all, all the O2 really does is amplify the signal in front of it, which means a great recording, a nice DAC and a stellar sounding headphone or IEM is what’s needed to put you on the path to #AudioNirvana.

    The best thing about the O2, sonically speaking, is its versatility. It has the power and dynamic range to drive anything from a sensitive IEM to a power hungry dynamic headphone with authority. The semi-picky Sennheiser HD650, for example, gets plenty loud and hits with modest authority in high-gain mode. The O2 can also play any genre of music well, because, well, you’re hearing the music and the rest of your equipment for what it is. The caveat here is that you need to plan for this. Meaning, the O2 is going to do absolutely nothing to hide poor recordings, and if you favor a darker, warmer sound signature, you’ll want to choose a headphone with those characteristics rather than something analytical like the reference level AKG K701. Or, you could always dabble with some EQ software to fine tune your setup. 

    With the OL/O2 combo, which is what I assume a lot of you reading this review are considering purchasing, you’re getting a pair of neutral performers, nothing more, nothing less. This stack isn’t going to romanticize your music collection. Rather, it’s going to allow you to focus on the music and hone your efforts on choosing the IEM or headphone that best suits your musical taste. 

    I’ve mainly been running the rounds with the Audioquest NighthawkBeyerdynamic Amiron HomeMeze Audio 99 Classics and Sennheiser HD650. The OL/O2 drives each of these headphones with ease and enjoyment, although none come off as being quite as airy, lush or three-dimensional as when pushed with a powerful tube amp (just my personal preference), the warm characteristics of each is conveyed cleanly and with good. Although these are all darker sounding headphone, I liked the pairings because it brought some balance to the neutrality of the OL/O2 stack. The consistent instrument separation and detail retrieval of the OL/O2 pairing is solid. The sound stage is modest, extending maybe three to four inches out around the head. Stereo imaging is dead center, although I do selfishly lust for a more holographic presentation. As someone who favors really lush sounding gear, this little stack can sound a bit flat to my ears—bass notes hit with impact, but often lack resonance; mids are clear, but are light on warmth; treble is crisp and detailed, and never too brittle, but airiness and texture seem overly controlled. But all of this is inherent in neutral, transparent solid state amps and DACs. Boring can also be better; the neutrality of this combo makes it an excellent setup for audio purists and gear reviewers because it reveals more accurately what a particular recording, headphone or IEM can and cannot do. 

    Overall, I generalize the OL/O2 stack as being crisp, clear, controlled and consistent. Sure, it can be boring for those that favor the ooey gooey goodness of lush and distorted tube gear, but boring isn’t always bad. In fact, these little black boxes are probably one of the best places to start for new budget-minded audiophiles looking to learn just what it is they like and lust for. 
      dr3wd4wg likes this.
    1. Jimster480
      Wow, really awesome review!
      I have been looking around for these sort of reviews as this is what I am looking into buying.
      I'm really debating between Modi Multibit + Magni 2 Uber or ODAC/Amp or Modi Multibit + O2Amp or E18K for now
      Jimster480, Feb 20, 2017
    2. SoundApprentice
      Thanks for reading @Jimster480 ... The Modi/Magni and OL/O2 are very similar in price and specs. Honestly, you can't really go "wrong" with either one. I'd look more at which one provides all the inputs you need and which suits your price point better. After you run either the JDS or Schiit for a while, you'll have a good feeling for what sort of sound you want to go after next, if you even need a next. Good luck!
      SoundApprentice, Feb 20, 2017
    3. Jimster480
      Thanks @SoundApprentice!

      The Modi Multibit is $250 by itself though and I would need a Magni 2 Uber which brings the cost of the stack to around $400 vs $250-300 for a OL/o2 stack.
      Jimster480, Feb 20, 2017
  3. boice
    Just as described
    Written by boice
    Published Jan 12, 2017
    Pros - Sounds Great
    Cons - Not super small
    I read about this device online and the reviews were very positive - so positive that I jumped in.  It was my first headphone amp — I purchased my second, the fiio a5, shortly afterwards.
    Take into consideration I am an amateur audio geek...
    It is just what everyone says about it; zero background noise; clean sound; no extra color.  I did also read that it was a little on the large size to be considered portable, and I agree that it is.  However it will fit in the back pocket of my Levi's so I'm still considering it portable.
    After comparing it to the fiio a5 for a week I must say I prefer the Objective2.  The "uncolored" sound is really more my style.  I wasn't sure where I fell on that spectrum...  But after comparing, I get it.  The objective2 is cleaner, more open.  You are not going to find something like a tube amp warmth.  But what you will find is your really great recordings in crystal clarity.
    Physically it's a nice solid piece of equipment.  It has a single red light when it's on.  The battery power so far seems to be in line with how it's advertised.  I do like that I can replace the batteries easily if I needed to.  Little things like that make this a special piece of equipment.  The volume control has a wide range so you can adjust it to very specific levels.  JDS labs has responded to my queries in almost real time.  They are very friendly and accessible.
      PanzerIV and stalepie like this.
    1. PanzerIV
      I currently own the (Fiio E12) and was considering an upgrade or wondering if I should get a desktop amp and keep my E12 strapped on my X5ii, and I was considering either the Objective 2 or the newer A5. I thought the A5 was totaly neutral too as it's what also the reviews and benchmark were showing. The O2 have a bigger soundstage and even more clarity? The specs of the A5 seems better though O_o
      PanzerIV, Mar 5, 2017
  4. aspro
    Excellent piece of kit (UK made model)
    Written by aspro
    Published Mar 4, 2016
    Pros - Size, performance, facilities(custom model)
    Cons - None
    I bought this to listen to my vinyl on my Hifiman HE-400 phones.  It does a great job of driving them with a very neutral and I can hear detail that my £5500 worth of amp and speakers don't pick up.  The JDS Labs would cost $191 shipped to the UK.  I bought a really nice version from a UK based eBay supplier (macwidow2011) - Swiss made board, neutrik connections, ALPS pot, RCA inputs and outputs with 1/4" jack - all for £109 shipped. 
    1. Sonic Defender
      Your speaker system is picking up that detail, unless it is quite old. The difference is that headphones are right on your ears so quiet details lost when sitting feet away from a speaker are easy to detect.
      Sonic Defender, Mar 4, 2016
  5. masterfuu
    In the amp jungle this little Tarzan holds its own
    Written by masterfuu
    Published Jan 3, 2016
    Pros - value, clarity, small footprint, runs cool, reliable, can drive many headphones
    Cons - could have more power for harder to drive headphones, could have more modern design, could use few other updates to bring this little Tarzan into 2017
    You know that feeling when you wake up in the morning and you can smell the coffee (Columbian, beautiful like their women), bagels (plain but fresh no manager specials) being toasted and birds singing (bunch of them in perfect harmony). It's the feeling of life just being right and problems being thing of past. That's how I feel today so I thought let's write a long overdue review of this little wonder called Objective2 headphone amp. There are many reviews with detailed numbers and measurements but my review is just my opinion based on many hours of listening all type of music with different headphones.
    My unit was purchased used for only $55 shipped here at head-fi few months ago. This is my second O2 amp first one was a JDS my current one is Massdrop made in China. Don't let the price tag fool you this little amp can't be beat for the money spent compared to amps costing much more. I had amps up to $2000 and unless your trying to power Hifiman 6 or certain planars your search can end right here right now. Do not waste your money do not fall for the hype because only hype real is the Objective 2 hype and that hype is real backed by measurements and cult like following over past few years.
    What makes O2 special is that it's a neutral amp (wire with gain as we call it) and it does not change the flavor of the sound . That is exactly how amps should be and rest of the gear so you can enjoy the soundtrack the way it was recorded in the studio and listen to headphones the way they were designed with their own sound signature. This little Tarzan has good power and is able to make most headphones sing including HD600, HD650, Beyer T1 (600ohm but fairly efficient). 
    Now is there a better amp out there? Yes, of course but requires you to spend at least six times of O2 price tag. While powerful, this little Tarzan could use slightly more power since I find some of my headphones slightly lacking in the lower frequencies but we are talking about very small improvements that takes good ear to evaluate.
    For money O2 is a slam dunk and one of most popular amps of all time for a good and well deserved reason. If you are trying to get your feet wet or just trying to find your final amp O2 will not disappoint most of audiophiles.
    Now back to last sip of coffee....  refill time. Let's load up on some more bagels. Oh snap, I'm out of cream cheese.
    If you find my review informative and fun please take quick moment and sub to my youtube channel:
  6. HiFi1972
    A DIYer's Dream Build (or you can just order an assembled one)
    Written by HiFi1972
    Published Oct 26, 2015
    Pros - Ability to build yourself, modification options, case engraving, customer support
    Cons - Would love for the LED to indicate low battery/charging
    You've already heard that the sound quality of this amp does not match its (low) asking price. You already know that it's one of the best SS desktop headphone amps you can get for your cans at any price point, really. So why am I writing another review on an amp that you KNOW is going to be awesome? Well, my review is for those who like to build their own amps and JDS labs is a company that "gets" the DIY movement and have made NwAvGuy's design really easy to build for those of us who like to roll our own gear. My review is meant for those who might be interested in ordering a DIY kit but who might not be sure of what they're going to get:
    Remember back in the day with the O2 was new and there were people scrambling to put together Group Buys for PBCs and components? Well, those days are OVER, thanks to JDS Labs!
    All the components come in their own plastic baggies, labeled clearly so you know where they go on the PCB. The PCB itself is of the highest quality you can expect as are the components themselves. All op amps and mosfets come in sealed anti static bags. For me, this kind of kit is a dream - I don't have a lot of time (or patience) to wait for people to put together Group Buys for an amp like this to save a few bucks. You would think that JDS labs would be marking up the cost of the DIY kit for this convenience, but frankly, they deserve a lot of credit for being able to provide the DIY kit for this amp for almost as much as it would cost you to go and buy the parts at a local electronics store, so the small "up charge" that you're going to pay isn't much at all when you consider how much time you're saving if you were to decide to spend a few days gathering the components yourself (and it might actually cost you more considering shipping charges and/or gas).
    I built mine using Cardas quad eutectic solder (the ones JDS sells are built using lead-free solder). I'm sure lead-free solder is fine, it's just my own personal preference to use quad eutectic solder for all my builds (and that's the nice thing, isn't it? You can use whatever solder or equivalent components of your choice for builds like these if the ones included aren't to your liking). It took me about 3.5 hours to put together the kit (PCB board and components, $60 at the time of this review). 
    At the time of this writing, there are no detailed instructions on how to put the kit together yourself on JDS Labs' website, but you don't need any really. Everything is labeled on the PCB itself, and everything is separated and labeled in baggies for you. There is however, help on their site for the various mods you can do (gain, RCA connectors, rear power, etc.) You do need to know how to install components for a build like this (like knowing which is the positive lead on a capacitor and which is pin 1 on an op amp, etc.) Adequate soldering skills are also necessary and I highly recommend a variable control soldering station for this kind of build too.
    JDS Labs' customer service is excellent. I've received responses to emails within a short amount of time and I've got nothing but great vibes from them with each response. Although I didn't have any questions concerning the build itself, they have been very responsive and helpful. I ordered an enclosure from them which I later decided to get laser engraved and they've been very helpful in answering file format questions, I'm sure if you have any issues with their kits that they'll be just as helpful.
    I'm so happy with my kit and interactions with JDS Labs over this Objective 2 that I'm going to be ordering more kits to build soon!
      PedroVazquez53 likes this.
  7. Hal X
    Tecnical perfection at great value
    Written by Hal X
    Published Jan 14, 2015
    Pros - (in my case I bought the kit)DIY. Perfect. Just the perfect wire-amp with no coloration or issues.
    Cons - None
    I own the desktop version of the O2. What to say? It is just perfect in every sense. No coloration , no noise, great power, best tecnicalities out there. BEST VALUE EVER. Endgame amp.
  8. YoYo JoKeR
    Objective2 : Wire with Gain
    Written by YoYo JoKeR
    Published Oct 9, 2014
    Pros - Sound Quality, Build Quality, Customization, Value
    Cons - Portability Issues
    The Objective2 is my first amp along with my beloved HD600 headphones. Here is my review after my experience with it for several months.
    Intro : I am an 21 year old Engineering student living in a small town in India. There is not much audiophile-community presence in India, Though lot of potential remains to be tapped. Auditioning an amplifier before purchase is almost impossible in India.
    I would like to call myself an music enthusiast, rather than an audiophile. I mostly listen to Bollywood and Indian Classical Music.
    I had bought off the O2 amp solely based upon its reputation, and also because of not being left with enough funds buy an more feasible amp.
    The O2 amp is designed by an famous American electrical engineer. It is well documented and measured amplifier, leaving no second thoughts on its performance. The goal of O2 amp is to achieve transparent sound with good measurements and at a reasonable price point, So that every enthusiast could afford an decent amplifier.
    The O2 can also be customized easily. It is available as a kit, or readily assembled, with/without case. It is cost effective and has many more add-on options.
    Design and Build : It is an very well designed and built amp. All components are mounted on an single PCB, with no manual wiring, which ensures longer life. It consists high quality double sided PCB, passive components, semiconductors and an Alps potentiometer. Exterior case has equally good build, with finished anodized and brushed aluminium case. Front and back panels are mounted by 4 screws, which can be removed easily to slide out the O2 board. All controls and jacks are mounted on front panel of O2.
    Overall,The O2 amp has Excellent build quality and design. Cant ask for more from an DIY amp.
    Sound :  O2 is very transparent. It has no ‘sound signature’ of its own. The output from the O2 depends very much on the source and ultimately on the headphone you are listening; it’s a wire with gain. It is an reference amp in sub 200$ price category, and comfortably competes with amps which costs much more.
    The O2 amplifies the input signals without adding any flavour of its own, which results in improved soundstage, dynamics and imaging. This transparent sonic character makes the O2 amp suitable for any genre of music. O2 has zero audible background noise and pitch black background. It has a very low EMI pickup, which is an advantage for Smartphone users.
    Output Power: Specifications state that O2’s output power is sufficient for most of the headphones. O2 amp can drive both dynamic and planar-magnetic headphones, though the latter seems much difficult to drive; The O2 takes the dynamic HD600 and planar magnetic LCD2  to loud listening levels, but ultimately lacks dynamics and power to ‘drive’ them properly.
    We know that the O2 can have custom gain settings. Though by default, the O2 comes with 2.5X/6.5X gain. Once the gain is flipped to 6.5X, background noise and distortion increases. I feel the gain switch is best set at 2.5X. But this again limits the O2’s output power for demanding headphones.
    The O2 amp has low output impedance and is hence is also suitable for IEM’s and earphones. One can hear an small ‘pop’ noise from headphones when O2 is switched on/off.
    Portability : The O2 amp is not sleek or light as the Cayin C5 or FiiO E12. The O2 is more of an transportable amp than truly portable.The O2 amp can work either on Internal Rechargeable 2X 9V Batteries or on External 15-20 VAC Adapter.
    Once fully charged, The O2 works on battery power for around 6-8 hours, which is quite decent. It doesn’t have any audible differences when running  on batteries or on AC Adapter.
    Slow recharging process in implemented in-order to avoid over-charging the batteries. Once the AC Adapter is connected to the amp, the battery recharging process is initiated. It takes around 12 hours to fully recharge the O2. There is no indication to the level of charge in the batteries; we have to manually estimate the approximate battery life remaining.
    Most of the portable amplifiers use 5V USB Charging. Whereas O2's AC Adapter is heavy, and is cumbersome to carry around. This further limits the O2’s portability.
    Though O2 is an excellent amp, but It's portability side suffers. If one wants to sacrifice the transparency of O2 for better portability, CAYIN C5 and FiiO E12  are pretty good amps, which have higher output power and are truly portable, along with very good sonic quality.
    Conclusion :
    The Objective2 is an fantastic amp, It is hard to beat O2 amp in its own category. O2 is an easy recommendation for an budget amp. Though not very portable, the Objective2 does its job and does it very well.
    The following features make O2 amp unique amongst others :
    1) Transparent Sonic Character
    2) Battery/Adapter operation
    3) DIY and customization
    4) Decent output power
    5) Easy maintenance
    6) Transportable
    7) Affordable.
    O2 is like an transparent window, which shows us, the view into music.
    1. PedroVazquez53
      My SennHD600 lack punch with the O2. I followed the instructions and changed the 4 gain resistors to very high gain. If you hear scratching or noise you can correct it by lowering the volume. The amplifier is powerful! I like to have extra power because it makes me feel that I can control the music when needed. If you want to know more you can contact me. Look at the instructions manual and consult the gain. When I was 15 years old every device used tubes. We had no problem with that.
      PedroVazquez53, May 9, 2019
  9. Hi-Fi'er
    Excellent in Price Category and Value
    Written by Hi-Fi'er
    Published Jul 1, 2014
    Pros - Light, Gain Switch, Replaceable Battery
    Cons - Not Lithium Batteries for More Power or Run Time
    I've been reading so many replies and reviews how the O2, Magni and Vali sound the same. After weeks of listening to all of them, (yes I have them all) they are all not exactly the same . I've been using the same music and all else in the system is the same and have only changed the amps. Started with O2, then went to Magni. Yes the Magni and O2 sound very close. The Magni does sound a tad processed and thin compared to O2 but the Magni does have more authority as it is more powerful in comparison even though they all seem to struggle reproducing the source. The O2 is a really nice amp but when compared to the Magni the O2 is better overall, but sound wise when compared to Vali in sound the Vali is a tad better.

    I hope this helps anyone who maybe interested in the O2.
    Update: I would recommend the Aune amp over the O2. Way more resolving, less distortion and is a true Class A amp.
      gab840 likes this.
    1. Evshrug
      Thanks for reviewing!
      I like that you distinguish the good qualities of the O2 and Magni, do you have a Vali review with details?
      Evshrug, Jul 3, 2014
    2. Hi-Fi'er
  10. akshayshah12
    Neutral Amp. Great Value.
    Written by akshayshah12
    Published May 19, 2014
    Pros - Flat sound. tight bass.
    Cons - Charging mechanism is pathetic.
    It lives upto its name. This ne is a gem as far as neutrality is considered most neautral Amp i have had or tried so far. I have tried HiFi man EF5 Fiio E11, E17 ,little dot mk2 etc. and found them clearly sub par comparing the bar this product has raised for its price. The immediate this one can notice is great improvement in both treble and Bass. Bass is quite tight. Treble is cold and accurate. Might sound little harsh for headphones like ATH50 but suits well enough for HD650. Wanted to try out well known tube amps especially Schiit Valhalla, Bravo audio ocean and the HD650 specialist (as per many folks on forums) Bottlehead crack. Unfortunately they are not easy to find in the part of the world i live. and i am not much into DIY either.May be someday i'll get my hands on them and then compare the famous tube sound signature with this little beast's accuracy in terms of SQ and see what suits my ears more, accuracy or the warmish (yet close to accurate) sound. For now i'd safely say this is best in class Amp and a great value.
    Let's look at its shortcomings.
    1. the charging mechanism has not LED indicator to show whether charge is full or not or whether it's charging or not for that matter. It  gets really annoying that i have to keep it off while it's charging and yet i don't know whether it is actually charging. It in fact most of the times is charging unless the heavy adapter has lose connection(it is quite possible as the adapter weighs more than O2 itself.)  or you forget to switch the button on (like i have done couple of times :p)For a 130$ product this wasn't a big feature to ask. 
    2. Gain switch is useless IMO as it totally screws SQ I never needed it though, HD650 can get enough juice on 2.5X gain setting. 


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