That would be consistent with the attenuator being connected backwards,
which would short out the DAC when set at minimum.
which would short out the DAC when set at minimum.
asking to understand not to dispute: I've used this attenuator for a week with these DAC's and a different power stage and it's been fine. If it were wired backward is it possible that it would be fine for other power stages but not the F5?
Editing to add: Just opened up the attenuator. It's an RK27 pot with the DIYaudio breakout board. Pot is correctly oriented on the board, In to In / Out to Out / Common strapped to the Out shields
Editing to add: Just opened up the attenuator. It's an RK27 pot with the DIYaudio breakout board. Pot is correctly oriented on the board, In to In / Out to Out / Common strapped to the Out shields
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Just checked again. It is wiper to output. Should be good.
so my previous schematic is wrong.
alrighty. Well, miraculously the Audio GD dac has a bad smell but no visible signs of damage. Still works and running now although I will be keeping a suspicious eye on it for a while.
I'm at a loss and very discouraged. I expected that this project would have plenty of things I needed to learn and correct and maybe a few broken parts, but I didn't expect torching my upstream.
I can still go back and install coax instead of braided single conductor at the front end but I'll be hesitant to plug in any inputs. Maybe time to buy up old Modi's and CD players on ebay.
I'm at a loss and very discouraged. I expected that this project would have plenty of things I needed to learn and correct and maybe a few broken parts, but I didn't expect torching my upstream.
I can still go back and install coax instead of braided single conductor at the front end but I'll be hesitant to plug in any inputs. Maybe time to buy up old Modi's and CD players on ebay.
Turn on the amp without source connected. Do you have any voltage across +/- of rca input jacks?
Yes. With one lead to the PIM ground and one lead to the test surface, the + and - of both RCA's measure 22v DC. Also all Ground components that are attached to the power supply board ground measure 22v DC.
Also compared to the PIM / wall ground, V+ sits at 45v DC and V- sits at -0.3v, which would still put them at 22.5V away from each other, if that makes sense.
Also compared to the PIM / wall ground, V+ sits at 45v DC and V- sits at -0.3v, which would still put them at 22.5V away from each other, if that makes sense.
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Not right, so stop using the amp until the problem is fixed.
The clue is that it only seems to work with floating sources.
The clue is that it only seems to work with floating sources.
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Understood. Other than biasing procedure it hasn't been on for more than 5 minutes today. It's fully unplugged and out of use now. I think I've spotted the problem on my PSU board. I'll report back shortly.
Deeply appreciative of all the help. It's a little embarrassing for me but I appreciate all the help.
Deeply appreciative of all the help. It's a little embarrassing for me but I appreciate all the help.
If you can get us good pics of the boards and wiring we can probably help further. But yeah, something aint right.
Could be wiring to the amp boards. Maybe two wires are swapped.
Everyone, at all levels of experience, has made mistakes.
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Alright I think it may be resolved.
From my PSU to CL60 to ground, I was running from the back corner of the board near one of the diode inputs. Not right. This meant that in relationship to the ground tabs on the board the PSU ran at +/-25v. But in relationship to chassis / power ground, it ran at 50v/0v. Swapped the cl60 ground scheme to the GROUND labeled tab on the PSU board (DUH) and powered everything back up, now in relationship to chassis / power ground we are +/-25.
Reassemble everything, do stage one of the biasing procedure, check RCA's and now there is no voltage on the RCA's.
Going to let it warm up again as per bias procedure, gently crank to 0.6v bias and try again tonight. We may have made it.
I will report back when I explode my next digital source.
In other good news, my Audio GD has been playing for 2ish hours with no problems and appears to be OK. I can handle 1 used Modi down.
From my PSU to CL60 to ground, I was running from the back corner of the board near one of the diode inputs. Not right. This meant that in relationship to the ground tabs on the board the PSU ran at +/-25v. But in relationship to chassis / power ground, it ran at 50v/0v. Swapped the cl60 ground scheme to the GROUND labeled tab on the PSU board (DUH) and powered everything back up, now in relationship to chassis / power ground we are +/-25.
Reassemble everything, do stage one of the biasing procedure, check RCA's and now there is no voltage on the RCA's.
Going to let it warm up again as per bias procedure, gently crank to 0.6v bias and try again tonight. We may have made it.
I will report back when I explode my next digital source.
In other good news, my Audio GD has been playing for 2ish hours with no problems and appears to be OK. I can handle 1 used Modi down.
Alright bias is set, no voltage on the RCA's, just subbed onto my rack and it's working great. I'm feeling a lot better. It's not mentioned much in reviews but my favorite feature about this amp is how it doesn't shoot DC into my source components.
Thanks again to rayma and hikari1 for staying with me through the dark night of the soul.
Thanks again to rayma and hikari1 for staying with me through the dark night of the soul.
I’ve burned mosfets, jfets, drivers, ruined caps and had one amp catch on fire.
Just tell yourself it’s a $4000 amp retail. You spend 1/4 of that on materials and a dac. Your still up $3000.
Just tell yourself it’s a $4000 amp retail. You spend 1/4 of that on materials and a dac. Your still up $3000.
True. I'm happy.
Would have been less happy if I lost my Dac 19 too just because I like it so much.
The other angle is that learning usually costs money and time. This build included a lot of new theory and skill building for me and that is a reward of its own.
Would have been less happy if I lost my Dac 19 too just because I like it so much.
The other angle is that learning usually costs money and time. This build included a lot of new theory and skill building for me and that is a reward of its own.
I see everyone using multiple meters when setting bias and DC offset. Is this just for convenience or is there a procedural reason? Can I get by with just a single meter? Thanks!
tuning P1 affects N and P bias and Offset - same does tuning P2 (and P3).
So you need 3 DMMs to balance everything.
Solid!
A.
So you need 3 DMMs to balance everything.
Solid!
A.
I'd advise against using just one meter, but it can be done.
One meter with standard probes ... likely frustrating...
One meter with a few sets of attached probes ... move the meter between sets of probes... may take a bit of extra time.
Multiple meters with a few sets of attached probes. 😀
One meter with standard probes ... likely frustrating...
One meter with a few sets of attached probes ... move the meter between sets of probes... may take a bit of extra time.
Multiple meters with a few sets of attached probes. 😀