What Does It Take To Turn The PC Into A Hi-Fi Audio Platform?

JDS Labs O2+ODAC Combo

The O2+ODAC that JDS Labs (among others) manufactures, based on an open source design, is the most innovative concept in our round-up.

In 2011, a mysterious blogger who used the handle "NorthWest Audio/Video Guy" (NwAvGuy) began ranting about the snake oil he believed was being sold to the audiophile community. He set out on a personal crusade to design and build a low-cost headphone amplifier that, through blind tests, could not be distinguished from the Benchmark DAC1.

That design eventually became what's known as the "O2" (from Objective2) headphone amplifier. NwAvGuy went on to create an implementation of ESS' ES9023 chip to function as a DAC feeding the O2, using similarly objective criteria. That latter device came to be known as the "ODAC" (from ObjectiveDAC). Both devices can easily be connected and integrated into a single enclosure.

The O2+ODAC is an uncommon design by most standards. The headphone amplifier, in particular, was originally designed with battery-powered operation in mind (for portability). While the JDS Labs implementation does away with the batteries, it retains many of the portability-related design choices. It employs an external AC transformer, not the internal one you'd find on most comparable DAC/amps. There are no RCA stereo outputs at all. And the O2 does not use an amplifier chip (like the TPA6120A2), but rather a custom design on the output stage.

Feature-wise, the O2+ODAC is really barebones. It has a 3.5 mm line-in connection up front, a mini-USB port in the back, and a 3.5 mm headphone-out jack. That's it as far as I/O goes. Controls are limited to a gain switch and an analog (high-quality) volume control.

Based on NwAvGuy's open-source license (which, paraphrasing, states: anyone and everyone can manufacture one of these without paying me a dime, as long as they don't change the design), a variety of manufacturers are now selling O2+ODAC devices.

In 2012, after being banned from the headfi.org forum for, according to his version of the story, criticizing one of that forum's sponsor's products, NwAvGuy started building a desktop-oriented version of the O2+ODAC, called the Objective Desktop Amplifier. The twist is that NwAvGuy mysteriously disappeared without a trace in mid-2012 before completing the ODA's design. Nobody seems to know why he stopped blogging or what happened to him. So we're left with the O2+ODAC to test, and a lingering dream of what the ODA could have been.

The manifestation we're testing today is provided by JDS Labs. It is sold fully assembled for roughly $290, including the required AC transformer. If you're nimble enough with a soldering iron, you can pick up the O2 do-it-yourself kit for $69, add the ODAC board for $99, and buy the transformer for $11. That'd get you going for about $180, not including the enclosure.

Aside from the performance commentary you'll find through the following pages, I encountered one specific problem with the O2+ODAC. After receiving and unpacking it, I clicked into high-gain mode, plugged in my Sennheiser HD 800s (300 Ω impedance), turned up the volume, and noticed that the sound was terrible, affected by massive distortion. It turns out that the supplied transformer isn't powerful enough to drive high-impedance phones using the high gain setting. Unfortunately, JDS Labs doesn't stock higher-power transformers, so a replacement wasn't an option. The only solution was to use the low-gain setting at much higher volume. That did successfully solve the distortion issue. But JDS Labs should consider, in my opinion, stocking AC transformers that better-support the high gain setting. Going one step further, transformers should really be included with the assembled product.

So, did NwAvGuy end up winning his crusade? Can the O2+ODAC be distinguished from the 7x-more expensive and 5x-larger Benchmark DAC2? Read on...

Update: We received the following response from JDS Labs:
"AC adapters for O2 are packaged separately because JDS Labs ships worldwide. There's little incentive to bundle AC adapters since each customer requires a unique plug. Thus, the items are presented separately for customer's selection. Our shopping cart reminds customers to choose an appropriate model. As of late December, we now stock a higher-power model for U.S. customers who need additional current; this represents less than 2% of customers, though. All European, Australian, and British AC adapters stocked by JDS Labs are high-power models."

  • SuckRaven
    Bravo ! Awesome, and a very thorough review. Even though as you mention, audio gear is not usually the forté/emphasis of the reviews here, it's refreshing to have someone at least try to cut through the (more often-than-not) overpriced arena of bullshit that is the field of "high-end" audio. I applaud the review, and the effort. Keep up the good work. More please.
  • PudgyChicken
    Just wondering, why not test a Creative X-Fi Titanium HD or something like that alongside the ASUS Xonar? It would be interesting to see some of the differences between different PCIe sound cards in this matchup. However I understand that what you were really going for was showing the difference between price point and form factor at the same time, so perhaps not testing two PCIe cards makes sense.
  • kitsunestarwind
    The biggest thing I have found for the PC is no matter how good your DAC is , if your speakers and AMP are crap, then it will never sound better.People spend big money on DAC's and forget that you need a high Quality amp with very very low THD (total harmonic distortions) and a very good set of Full Range speakers with high sensitivity if you want good sound, instead of crappy (albeit expensive) computer speakers especially sets with a sub.
  • shahrooz
    this article just won Tom's Hardware Readers Elite award
  • maestro0428
    Wonderful article! I love listening to music and do so mostly at my PCs. I try to set up systems where audio is important in component selection. Although we all love drooling over expensive equipment, many times it is not all that necessary for an amazing experience. I'd love to see more! Including smaller, studio speakers as I believe that speakers/headphones are the most important part of the equation. Keep up the great work!
  • blackmagnum
    Don't forget that for PCs: the hardware is as good as its software (drivers).
  • Someone Somewhere
    Agree totally with this. It always annoys me when people say they're spending over $100 on a sound card, especially when it turns out that they're using Optical out, and the whole thing is basically moot.I now have a nice source to link to.
  • 1zacster
    The thing is you can't just pick up two sets of good headphones, try them on different DACs/AMPs and expect to hear major differences, it takes longer than 5 minutes for your ears to adjust to newer headphones and for the differences to actually show. This is like taking food from Left Bank and then bringing in a bunch of hobos and asking them tel tell the differences between the foods.
  • dogman-x
    I use an optical cable from my PC to a home theatre receiver. With this setup, stereo CD audio content is sent as raw PCM to the receiver, not compressed into DD or DTS. These days you can buy a very good quality home theatre receiver for less than $200. Audio quality is outstanding.
  • Memnarchon
    I would love to see ALC1150 in these tests too, since its widely used at most Z87 mobos.