There are two opposing forces in high-end audio, especially digital high-end audio. The first is the notion that the best products can only be made by large teams of engineers, each an expert in their own little fiefdom of digital audio. The other holds a completely opposite position; that the best products can only be the result of one visionary engineer. The APL DSD-SR Mk2 is very much in that latter camp, being the brainchild of the adept digital designer Alex Peychev.
Of course, the reality is there is a lot of convergence between these two almost invented opposing positions, as even the largest design teams often report to an expert with the vision to guide the project, and the ‘one-man-band’ is often simply the head of a team of clever engineers. That all being said, the Bulgarian designed and built APL DSD-SR Mk2 is the kind of project that can only be made by ‘a man with a plan’. And Peychev – with his extensive background in pro-audio design (including several years as one of the lead engineers for Sony Broadcast and Professional Group) – could almost be the archetype for ‘a man with a plan’.
That plan includes practically everything a digital audio enthusiast might want from a DAC today. A purist circuit eschewing any kind of relay switching in the input stage or op amps anywhere in the audio circuit, the DSD-SR Mk2 features paralleled DAC chips, on board femtosecond low-jitter clocks and a fully transformer-coupled zero-feedback Class A output stage featuring top-notch Lundahl transformer for both balanced and single-ended output.
APL has also taken a very modular approach to the internal architecture of the DSD-SR Mk2, with carefully isolated power-supply, digital input, logic, digital processing and analogue output boards. This means if in the unlikely event of something untoward happening to the DAC, or the DAC itself requires a significant upgrade to remain at digital’s leading edge, there are lone boards to swap instead of a whole DAC needing a change. As it stands, however, the DSD-SR Mk 2 supports PCM to 32bit, 384kHz (S/PDIF to 24/192), and up to DSD256. If you use its built-in volume control (as in, using the APL as combined DAC and preamp), the 0.5dB digital step volume is non-decimating, so no nasty bit-chopping. There are no network options, however, and the DAC does not support MQA.