My opinion is -
(oh hang it, in for a penny..)
I have to say it looks all a bit bit perfunctory, the proverbial Mug's Eyeful. There's an awful lots of parts thrown at datasheet-based application notes with no real thought, for example a lot of electrolytics pointlessly-paralleled with small film types for the sake of it (regardless of whether or not it helps or makes a resonant mess*); there's no detail at all on the actual physical layout - the other 50%, the 'hidden' schematic that matters so very much when when working with HF and digital signals; and whoever plonked AD797s into that circuit did so because they wanted it to appear good on paper, without actually reading the 797 datasheet or ever playing with one to realise those extra parts and layout hints in the datasheet are there for really good reasons. Opportunities utterly unexamined, not merely tossed away here I think.
As a pile of parts to play with as a diy usb-input dac it actually may be pretty good value as a thing to tinker with until insane, perhaps worth a go if you want to indulge the time. But I bet your fettled Arcam Alpha even in its simplest incarnation would give it a solid kicking, out of the box or after you've been 'fixing' the dac for months
And objectively, spending a comparable amounts on the current Musical Fidelity V-dac )or whatever it's called) will buy you a working dac that measures superbly well meanwhile, is flexible, compact and future proof and comes with a warranty. You might even like it.
M.
*Alright, a simple example - look at the regulator schematic. Adjustable 3-pin regs with both 100uF, and a 0.1uF film cap in parallel on the output (no!!); then all followed with a 47uH inductor (why? to contain the mess you just made? It separates the HF film bypass from the circuit served if nothing else. So neither part is doing any goddam good, and wouldn't
even if they were physically placed to do any good. But given the contradictions I've littel hope of that.
- So then you probably have both an unhappy reg, and a thing uselessly raising it's output Z in the audioband, but there because it looks like 'low noise'. Smacks of pandering to the kinds of people who review with their eyes and no actual measurement. Frankly I'd rather see a cheap 7805 with cheapo CRC in front of it. Cheaper in parts and guaranteed to always work, and probably well enough until
proven otherwise. And even then - possible to get wrong if you dont route the reg's 0v reference directly to the 0v reference of the thingummy it powers.
And this kit has USB-ii2s conversion, digital filter and a dac requiring three good regulators to itself, all on the same board. Oh and a TCXO, a classic sign that the designer knows very little about what might matter. But it is shiney.
