subset or superset of the HagClock inside the HacDac
Actually not. I use a special VCXO in the HAGDAC (has to be variable). I did try to roll my own, but couldn't get enough range. It ended up turning into a HagClock circuit. So I spent the money to buy a really good VCXO.
The HagUsb didn't get a special clock for a number of reasons. First, I wanted to keep PC power and ground isolated from the audio system. Hence, I run only the S/PDIF output from it through a transformer. This keeps grounds completely separate. Two, the HagClock needs +/- supplies higher than 5V to work. Adding these and then isolating them from audio ground would have been costly. Third, having a good 12MHz clock does little for the quality of clock spit out by the USB chip. Too much crud inside the chip between input and output. Make sense? A perfect clock going in does not result in a perfect clock going out. Therefore, my solution to the problem (it's a system issue), was to use the reclocking capability of the HagDac to fix things. I end up with a super clean low jitter clock right where I need it.
jh
