INTRODUCTION

   Over the years although I’ve had both the pleasure and privilege of testing a very large number of earphones and headphones by numerous manufacturers in the market i never did ask for more since i always found that the volume levels offered by most models were more than just sufficient for my taste. However we always seek to expand our reviews so when some of you asked us if we could start doing headphone amplifier reviews i really found it interesting and so without delay we all started looking for the best solutions currently in the market. As usual i won't lie to you, there are numerous interesting models by many manufacturers currently available that can boost volume levels but one topped our search both in terms of quality and features, the O2+ODAC Combo by JDS Labs. Now JDS Labs doesn't make just one of these tiny devices so you can choose between 3 different models (black, silver and custom) the third of which you can partially customize according to your liking (and we did).

   JDS Labs brings you headphone amplification true to sound, all made in the USA. We go above and beyond American manufacturing. We built our in-house machine shop and production line to achieve product quality that we're proud of. JDS Labs's success comes from our obsession with brilliant audio engineering. Performance of our amplifiers and DACs pushes the market forward.

   The O2+ODAC (Objective2 headphone amp + ObjectiveDAC) amp+DAC combo is based on the original "open-source" design introduced back in 2011 by a blogger named NwAvGuy (his blog is still online) who claimed that he could build a low-cost device which could match the audio quality of the almost ten times more expensive Benchmark DAC1 in a blind listening test (he gets no profits but under his license manufacturers need to follow his design). JDS Labs however is not new in the industry since they were first introduced back in 2007 with their premade (and again open-source) CMOY headphone amplifiers and although i had the chance to take a closer look at one (looked more like a candy/cigar metal box) i never did use it. The O2+ODAC model however is much more than just a headphone amplifier since the integrated Objective DAC (ODAC) allows you to connect it with PC or Mac via a powered USB connector to get audiophile digital to analogue conversion. This sounds great and to be honest with all of you we can't say whether or not the O2+ODAC model actually compares with the DAC1 since we don't have that model here but what we can do (and did) is for all of us to test it and see (or better yet listen) how it performs.

SPECIFICATIONS AND FEATURES

PACKAGING AND CONTENTS

We received our custom O2+ODAC device inside a dark grey box with the company logo at the front and the country of manufacture at the rear (USA).

As you can see the packaging is basic so the device sits inside a plastic (could be also by aluminum) static-free bag.

Inside the box you will find the O2+ODAC headphone amplifier and DAC, 4 round silicon feet (which you can attach at the bottom of the device), USB to microUSB cable and the operating instructions paper (the AC adapter is sold extra).

THE O2+ODAC CUSTOM

Our custom unit arrived in black color and just like the others measures 108.5mm in width, 80mm in depth and 29.5mm in height and weighs 260g (weight may not be exactly the same due to different components).

Since I’m certain many of you wonder about just how large the O2+ODAC is we placed it right next to the compact REVO Wireless headset by Jabra.

The fascia of our custom sample is a little bit different than the two other available models since we chose a 6.35mm headphone jack instead of the typical 3.5mm jack. That aside we see the on/off button, power LED, volume control knob (metal and not plastic), low or high gain amplification button and the input 3.5mm jack.

Moving at the rear we see the microUSB port (used to power the DAC), left and right DAC line RCA output (something you also don't see in all versions) and the DC in.

Gaining access to the interior is not hard and so the first thing you will see (or better yet not see) is the lack of any kind of rechargeable batteries (as expected since the O2 and the ODAC leave very little room).

To stream stereo audio via the microUSB port JDS Labs has used the TE7022L USB 2.0 Controller which supports 16/24-bit resolution and up to 96K Hz sampling rate.

The 2.5/6.5x gain feature of the device is produced with the help of two operational amplifiers (JRC 4556AD Op-Amp model) also present on the PCB.

There are also a total of 6 capacitors on the PCB manufactured by the Japanese Nichicon Corporation.

CONCLUSION

   If there's one thing an headphone amplifier will definitely give you that's plenty of volume, at least much more than what you can get without it so right from start we all expected some degree of audio distortion which even after over 2 full months of testing (4 people used the device in total including myself) we didn't hear. On the contrary the result was superb with plenty of clean and deep bass with surprisingly balanced and exceptionally natural mids and highs. Of course not having used another headphone amplifier is a drawback since i can't really compare the O2+ODAC with other similar devices but i have used many A/V amplifiers (some of which cost way over 2k Euros) with several headphones and i really don't think this little device has much to be jealous of and certainly not in terms of audio quality (features are somewhat limited but that's to be expected from such a tiny device). The only issue some of you may have with the O2+ODAC is with the gain feature since even at 2.5x it just might be too much for your headphones (this also depends on the type of music) so if you happen to own a very sensitive pair you may not be able to use the device at its full potential (you can choose the level of gain however with the custom version). That being said we used the O2+ODAC with a total of 6 headphones from AIAIAI, Ultrasone, Jabra, Sennheiser, Sony and Thinksound without encountering any issues.

   You can purchase the black and silver editions of the O2+ODAC headphone amplifier and DAC directly from JDS Labs for a price of USD279 (plus 10.99 for the power adapter) so although not very cheap still it's many times cheaper than what you'd need to get in order to enjoy the same results. That being said our custom version with the rear mounted power jack, the 6.35mm headphone jack and the dedicated rear RCA line-outputs costs even more and climbs to a grand total of USD329 (plus 10.99 for the power adapter) but it offers extra features that i suspect most people will not have a problem paying something extra for. Bottom line if you seek to get one of the best headphone amplifiers in the market currently then you really should look no further than the superb O2+ODAC device by JDS Labs and that's why it gets our Platinum Award.

PROS

- Excellent Build Quality
- Size
- Exceptional Audio Quality
- Integrated DAC
- Two Way Adjustable Gain
- Ability to Swap Op-Amps

CONS

- Only AC Powered