Dac-Ah modified by Pacific Valve

[Dusty Chalk]

So I was leant a Dac-Ah for no other reason than to get my opinion. There seems to be some sort of distortion on it (I'm listening to Camille's Le Fil, and it seems to show up on her voice and the bass, and any other prominent sounds like that) -- is this something that will go away with burn-in, or is there something wrong and needs to be fixed. I forget which exact version it is, but could find out if it's important...or is this something that needs to be diagnosed on a case-by-case basis?

[luvdunhill]

So I was leant a Dac-Ah for no other reason than to get my opinion. There seems to be some sort of distortion on it (I'm listening to Camille's Le Fil, and it seems to show up on her voice and the bass, and any other prominent sounds like that) -- is this something that will go away with burn-in, or is there something wrong and needs to be fixed. I forget which exact version it is, but could find out if it's important...or is this something that needs to be diagnosed on a case-by-case basis?

does the distortion coincide with volume peaks? if so, there could be some clipping somewhere in the chain... or too wimpy of a power supply if it uses a wall-wart.

[tkam]

Well I know those TDA dac chips have pretty high distortion levels for dacs, but still it sounds more like a clipping issue. Or something is broken

[Augsburger]

I have a modded Dac Ah as well, though not by PAV and mine has no distortion what so ever. Most probably if it isn't a source issue then it is an errant soldering iron.

[Dusty Chalk]

does the distortion coincide with volume peaks?

Yes -- prominent bass and prominent lead vocals. The power supply is internal -- would that be wimpy?

Thanks all for the opinions -- I gave it back to the original owner to send back to Pacific Valve. I'll ask him in January if he's taken care of it yet, and then nag him until he contacts Pacific Valve.

[Pars]

I fixed a guy on Head-Fi's Musiland DAC for him and had to try to deal with Pacific Valve asking them for schematics. They were total assholes, even when we determined that yes, his came from them. And they are 6 miles away from me. Standard response was to send it in... probably for a board replacement ($$). The guy I did this for is in the Army and getting divorced AND with a kid... I wouldn't do business with them personally.

[dc]

a while back it was discovered that DAC-AHs were clipping because they had some wrong valued resistors because LM7806 regulators were running them @ 6v instead of the LM7808 it was designed for (obviously a clone gone wrong)

anyways, you could change the resistors or put some other ones in parallel (i forgot the exact values, they're on a thread somewhere) or do like others did and run them @ 8v with LM7808 regs

[Dusty Chalk]

How difficult would either of those be? My friend still hasn't done anything about it, and is not averse to having someone other than Pacific Valve do it.

And would you be able to tell if this is one of them from a serial number? Or pics of insides? What should I be taking a picture of?

[dc]

putting resistors in parallel would be easiest, followed by removing old ones and putting new ones in and finally installing new regulators and running them at 8v

if you run them at 8v however the performance is better but you will need to heatsink the 8x TDA1543 DAC chips and they will get quite hot

for me well i never experienced the clipping, but i was under there doing other mods as well so i installed new regulators

all the details are in this link: http://tinyurl.com/2fw9le

[Dusty Chalk]

Sweet, thanks.