Crack 5998 low volume

Adam,

Get some jumpers, alligator clips on each end.  Clip them to the test points then turn the amp on.  You can safely get the voltage readings.
 
Just realized....I can't check voltages, at least not tonight. I have to desolder my film caps to open the case, and I can't attach them when the case is open without a pair of leads with clips. Grrrrrrrr......
 
Adam,

This sounds to me a lot like your new tubes may have had some crap (wax?) on the pins and when you first inserted the one and then the other, you gunked up your socket pins.  Get some pipe cleaners, some round wood toothpicks and some kind of solvent like mineral spirits or 409 or something and try a good, deep cleaning on the sockets and then on the pins themselves.  If this is what happened the trick of pulling and inserting the tubes will do nothing.

Also, when using pipecleaners, have the unit off and unplugged and all charge drained off -- they are metal spines and you don't want to be zapped when doing this.

This is assuming that the LEDs are all glowing and that there is no obvious damage to rectifieers, etc.

HTH,

Jim
 
First,

Apologies to everyone for my rant yesterday. I was frustrated, and although I'm still frustrated for reasons explained below, I've calmed down a bit.

So....the issue wasn't the Crack at all. I went out, bought some pipe cleaners, cleaned the socket, and then tested the Crack with a portable source. It worked fine. So I put it back into my rack and hooked it up to my system via a line router. Only low sound again. I'll spare you the 20 intermediate steps used to diagnose the problem, but the bottom line is that the balanced outputs on my DAC work just fine, but the unbalanced RCA outs are only putting out a very, very, very low signal. I'll open it up to see what the problem might be, but if anyone has any ideas, I'm all ears. Could using signal attenuators have caused a problem?

Best regards,
Adam
 
OK, now I'm totally stumped. I opened e DAC. The unbalanced RCA outputs are just connected to the balanced XLR outputs and the wiring is all perfectly fine and intact. The balanced outputs work without any problem. The unbalanced don't. How is that possible? I even checked the unbalanced interconnects in a different setup. How is it possible for both channels to suddenly not work (or rather only work at very low volume), when the balanced outputs are fine? They are connected. If one works, the other should, too. I'm totally flabbergasted and have no idea what to do next.
 
Yes, it is. Good thinking...unfortunately, this model doesn't have a button to select between ACSS and other outputs -- all outputs are active all the time. You can only select gain and input. Besides, since the unbalanced outputs are wired to the balanced outputs, if one works, the other should, too.
 
The unbalanced outs are indeed wired to one balanced hot and ground. But the DAC puts out 5V balanced and 2.5V unbalanced. I've never had a problem using it this way before. The signal was plenty strong. If anything, it was too strong.

As for ACSS, I can't turn it off. I have other Audio-Gd DACs where you push a button for ACSS vs. RCA, but the Ref. 5.32 doesn't work that way. ACSS is always on, as are the balanced and unbalanced outputs. And again, I don't really see how it is possible that the unbalanced outs wouldn't work if the balanced outs do.

I thought maybe there was a cold solder joint or something, but everything looked fine and it isn't that the unbalanced outs don't work at all - if I turn the Crack or one of my other amps up all the way, I can hear a signal, but it is very, very faint. It's not 1/2 as strong as the balanced output - it is more like 1/50th or 1/100th. And I have this faint sound in both channels, not just one. None of this makes sense to me.

Please understand that I appreciate your help and brainstorming here. I just don't think we have hit upon the answer yet.

Signed,
Confused in Connecticut
 
Perhaps it's time to talk to Qing-Hua?  Sounds like maybe something went kahput with the dac's output section -- possibly.

Sorry it's so frustrating but at this point I really don't think it't the crack.

-- Jim
 
Your logic is perfectly good, so it is very likely one of your assumptions is wrong. Sorry that's not as much help as one would hope!

Is the interconnect good? Does it actually connect to the jacks at each end? With no shorts? Perhaps you could find a source of constant-voltage sine wave, and measure the output voltage between the balanced outs (should be 5vFS), from ground to each of the balanced outs, and ground to the RCA "hot". Repeat at every stage - DAC jacks, cable ends, connectors inside each target device, ...

Having seen a zillion of these kinds of question, I am confident you will find the answer eventually!
 
Question: if one of the hot signal lines to the balanced outputs were to have a really weak signal (e.g., if L+ and R+ were both weak, but L- and R- were both normal), would the balanced outputs sound odd when feeding a balanced amp? Would the signal be weaker, wonky or would there be no sound at all? I'm wondering if maybe that is what happened and the hot signal to the unbalanced outputs is somehow defective, which is why the unbalanced outs sound weird, but because the other hot signal is fine, the balanced signal still works and appears fairly normal?
 
Play a 60Hz tone through the DAC, measure the AC voltage between the hot and cold pins on the XLR jack, then between hot and ground and cold and ground.

This would be a nice way to verify that things are in order.
 
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