Finally! I finished two of these - probably the finest USB-powered DACs I've ever heard and among the finest overall, period, I think (bias admitted). I made some stupid mistakes along the way, but ended up with both of them essentially working the first time out, except for one particular stupid thing. The stupid thing was that I was so eager to get them clean and spent so much time rinsing them with alcohol that it left quite a bit of fluid under the chips (unbeknownst to me). They kept cutting out on me yesterday at random and driving me crazy trying to figure out what was wrong. Now that they're dry, there's been no hiccups at all - just clean, sterling sound with more bass, more highs detail and resolution than the earlier pupDAC, and that same seductive mid-range.
As for the offset, I think we're saying that cobaltmute's version may be a fluke. Mine measured 1mV on the left and right RCA jack (referenced from the "GND" test point) with one pupDAC and 0mV left and 1mV right on the other pupDAC. So, I don't think we have an issue with offset.
My understanding with cobaltmute is that very little will change on the final production versions - just a bit of spacing to work out. The RCA jacks either need to have their front pins sliced off, or you need to carefully roll and force them into position onto the front edge of the PCB (what I did). Also, the Mica capacitors are too big for the lead spacing on the PCB, but I found if you pull the leads with a pair of pliers, you can get them down pretty close to the PCB surface. Finally, the C10 electrolytic is too close to one of the Mica caps, but all you need to do is bend it forward slightly to clear the electrolytic. The pads for the PCM chips have the same clearance as the original, so they are a bit challenging.
Needless to say, these are not beginner builds. I actually destroyed one PCB before completing these two (OK, I was out of practice, I admit). I have 5 PCB's left and they will go to 5 of the following people who've already expressed an interest earlier in this thread:
Avro_Arrow
forsakenrider
Misterrogers
c12mech
scootsit
Mullet
However, you MUST PM me through Head-Fi and confirm that your interest is still valid, and send me your NAME and ADDRESS. Price will be $20 plus postage payable to Paypal (the PCB's cost me $15 each from Imagineering), but that will include all three output jacks, since those were the only parts ordered from DigiKey instead of Mouser. Also, I will attempt to supply all the PCM1794 chips and as many PCM2707 and TPS chips as I can (I have several of each, but not sure if I've got 5 of each). Note that the PCM1794 is $13.62 at Mouser, just by itself.
First come, first serve!!!
P.S. Many, many thanks to cobaltmute for such an excellent design!!!
P.S. 2 - Looks like I missed one user, so there's 6 and only 5 PCB's - First come, first serve!
