After reading Steve's articles regarding computer audio posted on Positive Feedback, and having become, through those articles, persuaded by Steve's experience and evident accomplishments, I purchased a DEQX crossover/correction unit and sent it to Steve to mod the output opamps and to install a USB --> I2S interface on the input. I've listened to the final product for a few months and now can relate my settled view of its sonic qualities.
Upon first play, and for quite some time after, the unit sounded edgy and bright. This edge of course receded during what amounted to an appreciable break-in period. One factor prolonging the break-in was likely the presence of a large quantity of Black Gate capacitors Steve installed as coupling caps in the opamp section (Black Gates are notorious for requiring almost unlimited break-in time). The particular DEQX version I sent him was evidently an early unit, allowing space for only Black Gates + no film bypasses, and allowing no use of (large) teflon capacitors anywhere including bypassing opamp PSU traces. (My comments below should take this fact into account.)
After running the unit off and on for several weeks, I began listening critically. The original edginess had reduced significantly, but had not disappeared. I had some difficulty characterising the nature of what I was hearing, as the unit was very evidently a strong performer in almost every sonic realm, but for this one niggling, distracting problem. After some experimenting, I discovered the source of the edge, or the source of most of it, which was the power supply of my desktop computer. To my surprise, when I substituted my laptop for my desktop as digital source, the edge virtually vanished. Further experiments showed, to my ear, that a desktop fed with clean electricity sounded better than the laptop. It is with this setup---desktop plugged into extensive AC conditioning---that I was able to pinpoint the source of the (remaining) edge I heard (which I speculate to be jitter deriving from dirty AC powering the hardware feeding digital data into the USB pipeline).
So what does Steve's USB --> I2S link sound like in this slightly ancient, upgraded DEQX? In a word, it is the best digital---best sound---I have had the opportunity and pleasure to hear. After 20 years seeking the best sound I could find and afford, I feel I have finally approached---certainly to within throwing distance of, possibly within arm's reach of---the limits imposed by the source recording. I won't detail the litany of relevant sonic parameters---channel separation, clarity, purity of tone, freedom from fatique, presence, realism, bass drive, imaging, detail, smoothness, etc., etc.---because concerning each I merely would say it's the best I've heard, period.
This is not to say I think my stereo chain is perfect. Many elements of this chain can be improved somewhat, including improving opamp coupling in the DEQX, scrapping the mylar output filtering caps in my dual Tripath amplifiers, dual-monoing my pre, and changing a few other items I'll surely get to. Everything else is at a high level. My speakers are Aurum (read: Raven) ribbons + 4" Skaaning midwoofers in maple boxes, all wiring, incuding hookup wiring, is almost exclusively high quality silver, including Empirical interconnects, my Tripath amps are fed by teflon capacitor bypassed high quality Tamura smpss, coupling capacitors are my own teflon-beating Fluorinert designs, my preamp is the 6 channel Emm Labs (modified with Shottky bridges + many teflon bypasses and Black Gates), every component is fed by its own dedicated, insanely conditioned AC line. But the jewel in this system is its unassuming source, the DEQX.
Thanks to Steve for a wonderful product. Guys, there aren't many people out there with Steve's qualifications. I'm personally glad he turned his attention to audio.
[By the way, I've owned several amplifiers I've listened to, modded to better enjoyment, then replaced along the way---Edge NL-10, 572B SET (c-core transformers throughout + no electrolytics and no cheap films), Pass Aleph, conrad-johnson, Marantz, PS Audio. I'm currently finishing constructing a spud 6C45P using regulated smpss etc. as the last opportunity for tubes to displace my current preference for class D. YamplifierMMV.]
