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  #1  
Old 10-18-2011, 04:54 PM
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Andy_H Andy_H is offline
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Troubleshooting Xiang Sheng Tube DAC-01A

I just bought (used) a Xiang Sheng Tube DAC-01A. This is basically the same design as the Grant Fidelity Tube DAC 09 and the Maverick Tube Magic DAC as far as I know. I've been playing with it a bit, trying all the inputs and functions and it's not working 100% right. Sound through all sources/inputs (digital coax or Toslink, analog in via CDP) is imbalanced with the right channel noticeably louder than the left. If I swap the output cables this reverses (left channel louder than right). This is the same on the tube and ss outputs. The headphone output is fine though.

The seller tells me he was using it right up until he sent it to me and it was working fine, and I believe him. Although it did not show any evidence of shipping damage, my first guess is that something got shaken loose in transit and the trouble is an intermittent connection somewhere. It appears to me that the trouble must be in the output section and not the DAC or pre as the headphone out is OK. And the sound quality overall is good, just off balance volume-wise.

I pulled the board and looked for loose wires or bad solder joints. Nothing obvious immediately jumped out at me. I did read that there can be some kind of hiccup in the circuit that mutes output when you plug in headphones and that plugging and unplugging the phones a couple times may clear it up. I will try that in a bit here. If that doesn't help, does anyone have any ideas or suggestions of what to do? Thanks in advance.
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Old 10-18-2011, 05:34 PM
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w1jim w1jim is offline
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I've got one of those with no problems.
I assume you have nothing else plugged into the outputs.
Does it have the problem from both the tube output and analog outputs?

I'd try pulling the tube and seeing if the problem persists on the analog ("normal") output for starters. This could indicate a bad tube (damaged in shipping).
If yours has sockets for the op amps (I know that some do - I had to put them in mine myself) I'd consider swapping them but I'd first suspect the tube.
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Old 10-18-2011, 07:45 PM
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Andy_H Andy_H is offline
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What do you mean by "nothing else plugged into the outputs"?

I'm having the very same issue on both tube and 'normal' output jacks. Just for grins I did pull the tube to see if it made any difference, which it didn't. That was the first thing I thought of, was that the tube might have been damaged in shipping, but this appears not to be the case.

I had read that on some of the Grant-branded models there had been issues with channel imbalance that was due to a sticky relay that muted the outputs upon plugging in headphones, but mine doesn't mute the line outs when the phones are plugged in. Plugging and unplugging the phones doesn't make a difference.

Opamps in mine are directly soldered. If I end up having to swap any I will replace them with sockets.
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Old 10-19-2011, 12:21 PM
Mmaxed Mmaxed is offline
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I recently moved the jumpers on my DAC-09 (to put it into pre amp mode) and had the same problem. On mine it was poor contact between the jumper and the pins. Finally scuffed the pins with fine sand paper and bent the contacts in the jumpers to make them slightly tighter on the pins. Been good for a couple weeks now.
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  #5  
Old 10-19-2011, 03:17 PM
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Andy_H Andy_H is offline
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This one came from the factory without the preamp function enabled. Looking at the instructions from the Grant Fidelity website on how to mod for preamp use, the one I have is listed as the third version in the instructions. Rather than plugging in some different wires, one has to desolder a couple connections and reconnect at different points. I had decided not to bother with that right now for fear of messing up something more, although now I wonder if I shouldn't try moving the preamp jumpers just to see what effect that might have.
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Old 10-20-2011, 05:16 PM
Mmaxed Mmaxed is offline
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Yours is different than mine. Mine is the vs 2 so you just move jumpers to different position on pins. Poor contact there was apparently my problem so that wouldn't apply to yours.
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  #7  
Old 11-12-2011, 06:18 PM
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Andy_H Andy_H is offline
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Well, I finally got around to working on this DAC some more, and it turned out to be a $1.59 fix, and that was spending more than was strictly necessary. I pulled the DAC output opamp (U5 on the board), soldered in a socket and replaced with a new LF353 (the stock IC). I bought some other opamps to roll, and I'll socket the headphone amp (U6) as well, but I had to get it working right before trying any more mods. I think I'll convert it to preamp mode while I'm working on it. But anyway, if your Xiang Sheng / Grant / Maverick DAC starts acting wonky that opamp is a good place to look for trouble.
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