If you're doing a Logitech device the USB solution is out. IMO, USB isn't there yet, but that's based only on what I've read from (many) others. Plus, the Logitech solution is way more portable and is its own electrical universe, apart from the computer. I doubt there's a more electrically dirty home device than a PC and this is a good thing.
One of the biggest problems with 'conventional', separate transport/DACs is the s/pdif interface. Not only are the clock and data signals traveling the same cable, but because there is no impedance matching, clock signals actually bounce around inside the cable and further confuse The Clock. The reflection problem is why ART's digital cable is 15 feet long and uses BNC connectors which are 75-ohm matched. He says it helps quite a bit but don't get him started on s/pdif.
Actually, most transports have clocks and so do the DACs. So the transport is sending a clock signal, the DAC receives that data and tries to reconcile the two streams. The clocks, of course, do not synchronize perfectly. Result? Jitter. Pro gear often has a 'master clock' which coordinates these functions, as do some top-end manufacturers like dcs and Esoteric. I would imagine the PS Audio
system takes clock synchronization into account which is likely responsible for some of its acclaim.
I asked Vinnie at Red Wine Audio one time why I preferred non-oversampling DACs. His explanation compared a normal car with the same car with tons more horsepower. The normal car does its job effectively without strange side effects - the hopped-up version has much less margin for error.
I went through a good number of DACs before gravitating toward NOS units. My favorite was the Altmann Ugly Betty (not the real name but SHOULD be). Such a nice, talented, homely girl. It ruled the roost until I got the Lessloss paired with a clock-linked CDP. It uses two digital cables, sending clock signals to the disabled transport and receiving music data.
It's better, by quite a bit. Without delving into the usual blahbedee dah, it's huge resolution plus very low digital nasties. They're not abolished completely in my setup, if I went a little softer on my tube complement I could eliminate them but that would give up resolution I'm not ready to lose.
BUT you say, I said computer audio!! Oh yes, getting to that. It turns out the transport clock linking is a relatively simple process for any competent practitioner (not me). I already had three Squeezeboxes, sent one to Vinnie for the operation. He's not doing this service but anybody could. He talked to Liudas at Lessloss, it was a simple operation that's been completely stable for the last couple years. As far as I know, I'm the only one anywhere that has this combination which could mean I'm prescient or a dying/dead branch on the evolutionary tree.
IMO, it's the best of all possible worlds. I even just downloaded the $4 SqueezeCommander app for my brand new Droid Incredible and HOLYFRICKINWOW!!! It's at least as fast as my laptop as remote, better screen, fits in my pocket. You Apple guys have the Ipeng app which is at least as good.
I don't really understand any of this stuff, this is all just my conglomeration from many hours researching and conversing with knowledgeable folks. My guess is that 'this DAC' versus 'that DAC' is hugely dependent on synergy. Like preamp/amp impedance or an amp/speaker interface, the match predicts the outcome. Unlike those comparisons though, there aren't handy impedance, sensitivity, or other measures to narrow the choices. I'd even guess that
individual pieces of a particular model may perform differently as I seriously doubt every clock performs exactly the same. This is gross speculation though.
It's a real shame the Lessloss DAC hasn't gotten more press. Everywhere I've seen comments, they've been positive. Danny Kaey got the review piece after I finished with it and he's still using his as reference too. He just had further comments not long ago about it. Reviewers don't keep stuff for years, almost ever.
Asynchronous, synchronous, upsampling, oversampling, everyone says they've solved the jitter problem. IME the claims don't translate to earholes.
As usual, I can't keep my comments brief. At least they didn't cost you anything.
