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Empirical Audio Overdrive DAC

Posted by Thomas James (A) on October 5, 2009 at 14:42:51

I'm a happy owner of an Empirical Audio Overdrive DAC Signature, and thought I would note some impressions for others as another hat in the ring to aid (and possibly complicate) DAC purchase decisions.

I've been following Steve's products since approximately his entry into computer audio. I was initially impressed by his Intel experience, and appreciated he sold his products without the expense of a distribution chain. I have purchased a few of his products over the years, the most recent being the Overdrive DAC.

For impressions I note below, my setup was this:

MacBook Pro with SSD ---> Amarra ---> Lotus USB Cable ---> Overdrive DAC ---> balanced out to Sennheiser HD800 headphones, balanced mode

All equipment was plugged into an Accuphase power conditioner, itself plugged into an Elgar conditioner for series, double whammo conditioning. : )

In my many years of playing this audio game, this DAC produces the cleanest, most musically honest sound I have heard. The first thing that struck me on first setting the unit into play---and this without proper break-in---was the DAC's crystalline resolving power. Wow, I have not heard such clear delineation from any other piece of equipment I've owned. Leading edges sound wickedly fast and clean, considerably avoiding the typical smear, fuzz, incoherence and noise I hear ubiquitously in transient playback. I suppose noise in general must be kept to very low levels in the DAC, because its sharp transient reproduction comes at no expense to low-level detail.

In addition to crystalline transparency, this DAC resolves harmonics exquisitely. I often listen to Tord Gustavsen to test a unit's harmonic rightness. With the Overdrive, the harmonic bloom I hear is as if my head is inside Tord's piano.

These qualities, among others, combine to give a sense of spaciousness and delicacy that often leave me feeling I've encountered something beautiful in a listening session. Having spent as many years in this audio game as I have, I don't say that lightly.

With the same setup using the same balanced-drive Sennheisers, I compared the Overdrive to a Playback Designs MPD-5 DAC I have in my possession. The MPD-5 is of course touted as a leader in the DAC-pack, as rightfully it should be, I suppose. It's designer is Andreas Koch, who designed the latest Emm Labs gear which has garnered respect in the audio world. I've owned Emm Labs digital gear, and from memory consider the MPD-5 the better electronics. Here are a few links for those interested:

http://www.positive-feedback.com/Issue39/playbackdesigns_mps5.htm

http://www.audioasylum.com/forums/hirez/messages/24/246366.html

Comparing the MPD-5 to the Overdrive, I clearly prefer the Overdrive: it's clearer, cleaner, more resolved, has a more delicate, engaging sound. I judge the difference between the two DACs to be less than that between Amarra and iTunes, though the ways in which the Overdrive betters the MPD-5 reach into those very subtle levels of musical reproduction that, to my experience at least, hold the greatest emotional power. I consider it no easy feat to gain those extra few percentage points of reproductive accuracy. In my scale of value, adding those teeny points of percent at the upper reach ain't a diminishing return.

One note: the Overdrive's bass reproduction sounded comparatively lighter, but I think this is a product of insufficient capacitance on the output capacitors for the lowish impedance my Sennheisers present, and something I will cure myself once my latest batch of liquid-fluorinated teflon capacitors is off the production line. Other user comments suggest the Overdrive's bass is actually a strong point; I don't doubt that.

Going beyond mere sonics, the Overdrive scores with its fine volume control, which is non-switching. Over at DIY Audio is a thread on the Lightspeed Attenuator, which uses a non-switched (hard soldered) LDR attenuator. The designer claims to have measured deleterious effects of switching low-level audio signals. Having built a Lightspeed myself, and considering what Herve Deletraz says on the matter, I tend to agree. I've avoided switches ever since that experience (I use Lyngdorf electronics in my speaker setup).

For the MPD-5, volume must be controlled using Amarra. Given this, all comparative listening between the DACs was performed at full volume for the Overdrive and at -6dB on Amarra for the MPD-5 for volume matching. Turning the volume up to 0dB on the MPD-5 didn't change the character of the sound, resolution, dynamics, etc. This attests to the very fine operation of Amarra.

Of note, the Overdrive uses a Superclock 4. I have a Tascam/Pace-Car/Ultraclock setup waiting to intall into this system, but Snow Leopard has prevented Amarra from recognizing the Tascam. I expect a nice sonic upgrade once this little glitch is solved. Also, most of my listening was performed with two Paul Hynes supplies replacing two of the three switchers supplied as the stock power sources. The Overdrive does well with its stock supplies (still beats the MPD-5), but performs a little more gloriously with the Hynes units supplying power.

And finally, to the extent I can compare listening through headphones versus my regular setup (Lyngdorf Millenium, Weiss AFI1, Hansen speakers, gobs of teflon capacitors, more power conditioning), the Overdrive experience wins handily. Except for dancing.

And as with all things audio, YMMV. (But I doubt it.)

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