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CAD's got form. They're extremist computer audiologists who do just one thing but pursue that very thing to its ultimate end. Hence their shunt-regulated power supply isn't singular. It's as discrete as can be and a quintet of supplies each fed from its own custom-spec'd toroid. No multi secondaries for Scott who spent years perfecting these ultra wide-bandwidth supplies for being perhaps 70% of the final sound.


"USB's carrier frequency becomes 250MHz if we translate the usual 480Mb/s spec into the real-world 250.000.000 bits-per-second speed and transpose that into the frequency domain. This requires very different supporting circuitry than traditional analogue which was concerned with 20Hz - 20kHz." Therein lies Scott's preference for eliminating all switches. It also explains his excessive concerns over UF noise and slew-rate steepness. And don't get him started on optocouplers for galvanic isolation. He finds them sonically... well, pathetic. "My ideal scenario would be an ultra high-speed very short wireless connection of the sort we don't yet have between computer and DAC for the ultimate in isolation."
Standard TDA1543 block diagram with operational output amplifiers which the actual 1543 DAC of course doesn't use.

Because his USB transceiver doesn't run USB power—Scott shudders at the very thought—his personal USB cable naturally does away with a power lead altogether. Multi-paralleling his chips not only ups signal strength, it also expands dynamic range. "Noise doesn't scale up as does output voltage". Data happiness extends to 24/176.4kHz to process most currently meaningful high-resolution files. The deliberately modular assembly means that future upgrades can be implemented as they arise and even the rear panel replaced. Whilst Scott does acknowledge the mild treble roll-off endemic to his NOS scheme, he counters that to date none of his clients have complained.

On the old ΔΣ Delta-Sigma versus R-2R argument, Scott is obviously firmly in the latter camp. He thus considered the mythical BB1704K and experimented but found the Philips 1543/N2 sonically preferable. Given inevitable dealer requests for additional socketry, Scott is firm. "Although I worked on it for quite some time, I never found an S/PDIF interface that sounded as good as my USB. Hence it was USB or nothing." To get operational requires installation of his custom M2Tech driver for both Windows and Mac.
To get more specific on certain solutions which he believes give him the edge, Scott remains strategically mum. "None of it is any voodoo. It's just a solid understanding of high-speed circuits from my Tektronix days and much prototyping. As is intrinsic to the NOS approach, many things we can measure don't necessarily mean what we might assume. And as for things we hear, we often can't execute fully collaborating measurements. Computer audio is far more than just strapping a USB cable to an aging laptop and hoping for the best. But done right it enjoys results which exceed what legacy CD players could deliver. That was the entire rationale behind launching Computer Audio Design." This converter thus could be tailor-made for the vinyl/hornspeaker/valve crowd whose reference etched into their very bone marrow is vintage analogue.
  
Oscilloscope from Scott's old employer Tektronix whose motto is "from nano volts to Gigahertz"
 
The digital board with its twin rows of 8 x 1543 DACs all topped by a massive heatsink.
For them we might paraphrase a recent email from Definitive Audio's Kevin Scott to a reader inquiry: "Nothing good I know comes out of a computer." Nothing much does indeed if one won't properly configure it for just music. The crux is knowing what it entails exactly - a still ongoing quite steep learning curve. Basics include separating the OS from the music drive; defeating background processes; installing and properly configuring music players; running sufficient RAM and more. Recognizing the need for education particularly with dealers and reviewers who were steeped in analogue but never made a full transition into the computer age, Scott's routine involves bringing his own computer. Now that design work for the 1543 is a wrap, he plans on building out his website into a resource for computer audio information.

NOS DACists—makers and users—cite organic flow in contrast to the subliminal choppiness they perceive with modern digital. It's about a particular textural softness not synonymous with resolution loss or blurred transients. The core claim is quite simply for 'more analogue'. That's not hearing more but differently; a new gestalt or delivery feel rather than raw content quantity. RWA and AMR even offer switchable chips for vintage and modern.
 
The 1543 DAC's core audience might be those perennial malcontents who find fault with the digital medium even though they might no longer be able to put a clear finger on why. The focus here simply isn't swapping discs but transitioning from vinyl straight to PCfi. For CAD that tracks how its designer's and his lady's listening evolved. "We met over audiophilia" shared Isabel whose former day job was as oil trader. "I was one of our local dealer's very few woman clients who regularly bought expensive hifi to the tune of what a small or big car would cost."