Give Up?

Put a new DAC in. Speaker starts cutting out. Amp starts clicking.
Quick, what's the problem?
That was my experience today.
Any armchair tech assessments?
I did find the issue, and I'll confirm it when it's correctly identified.
Sounds like a few possibilities:

DC output from the DAC wreaking havoc.
DAC and transport are not linking up and the amplifier is going in and out of protection mode.

Take out the new DAC, replace with old and see if the problem reoccurs. If it does not, the problem is your new DAC and I would call the dealer you bought it from or the manufacturer and have them troubleshoot the problem.

If you want to call me, I would be more than happy to help you diagnose it.
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Maybe it didn't like your choice of digital cable... or it caught a power-line spike and a chip freaked out in which case unplugging it and plugging it back in could have "fixed" it...
Good guesses, but not correct yet.
I have the solution/answer and the fix already; I appreciate advice, but the situation is already corrected. I just want to see if anyone can guess what the problem was. Just a fun system "brain teaser" for enjoyment.

So far, no correct guesses. I did not screw up; there was a technical problem.

The prize is the satisfaction of being an audio genius and the endless admiration of the community. (Is that enough?)
Cold, Cold, all responses cold so far!
You begin to see that this was beyond a simple misconfiguration issue. This was a tube DAC, but it was not a bad tube.
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I had a similar incident with my tubed DAC a few years ago.The DAC was ARC DAC-3 and was bought used,it came with bad 6922 tubes.I first thought it was the pre-amp at fault because every time I touched the volume,cracling noise heard from the speakers.I actually sprayed the volume pot with Craig cleaner.Finally I realized it was the DAC and sent it away to ARC.They replaced the tubes and a few other things.
You don't give us enough information to work with.What was the problem?
Most are guessing the DAC. It wasn't the DAC. I exchanged it for a different one and the problem persisted.
The answer lies outside the (DAC) box! :)
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Did you accidently hit the speaker cables on the amp while installing the DAC, shorting them together?
Ok, well... Not my intention to "tease" about this, so here's the account. I would have thought someone might have suggested to "follow the chain" through the system.

DAC arrives and is installed. As stated before, the symptoms of cutting out and amp "clicking" begin the first time I use the DAC. The unusual nature of the speaker drop outs is that at very low levels (under 12 on a digital readout of 100 max) there were no drop outs.

I always power up equipment in a new rig in a safer mode, i.e. mute, then bring up volume slowly. So, in this case, as I bring up the level slowly everthing is fine, until I pass 12. Then the left speaker begins to cut out and the amp switch/click. The low level at which the speaker continued to play perfectly added to the difficulty in diagnosing the problem, as will be seen.

My assumption was that the DAC was damaged in transport; there was a pushed in corner where it had fallen, but no visible damage to unit and it was packaged extremely well.

I try the tube swap, to no effect. So, to rule out the DAC I remove it from the rig. I replace it with a different DAC and obtain the same results.

The problem persists (amp still clicking/switching), so I suspect the amp is damaged (by the DAC? Not likely, but can't be sure...). I remove the amp in question and replace with another pre/amp. Now the clicking of the amp has disappeared, but the left speaker is still cutting out! Can't rule out the first DAC as causing a problem in the first amp, but the odds of the amp being damaged now are greatly reduced.

Next, I test the cdp, since it's the source upstream and could be feeding the bad signal. Not likely to cause an amp to switch/click but must be ruled out to obtain a definitive answer. To check this source, I switch to streaming audio fed directly into the replacement pre/amp. The speaker cutting out remains, so the cdp has been eliminated as a potential cause.

I have at this point cleared only one component (besides the second DAC, which played no part in the initial problem), and that is the cdp. The DAC could still be the source of the problem, and the amp could still be damaged.

Now I am down to skeleton rig: streaming audio to the second pre/amp, the cabling and the speakers. I do NOT want to discover something shot with the speakers! But, I'm at the point of checking them now. Here is where the diagnostics got tricky.

I had listened to the speakers up close initially at a lower level, just enough to make them cut out. I assumed (here is where I was misled) that the entire speaker was dropping out - the speakers are biwired. I had put my ear up next to the mids/treble and could hear the drop outs. I did not hear any bass. That is because the low listening level (after all, I'm not going to blast a speaker that's cutting out and put my ear up to it!) and the extremely low frequencies emanating about two feet below ear level. The other speaker is playing fully and is masking the lowest bass output of the speaker I'm diagnosing.

So... I'm now down to the speaker as possible cause. I remove one cable and test one set of posts at a time, first the bass and then the treble. Now I hear each of them dropping out as the level is raised, not surprising since I had not detected the woofers still running prior. I then switch to the second set of cables and repeat the process. This might seem unnecessary, yet to rule out all possibilities it must be done. WALA! This cable performs perfectly at all levels!

To confirm the diagnosis of one faulty cable in a biwire set on the left speaker I replace the suspect cable and add back in each component. Perfect performance from every test. The speaker no longer drops out, the amp no longer clicks, the new DAC is flawless.

It was a speaker cable which I had not touched when I put in the new DAC! It happened to fail at the moment when the DAC was put in, so I had to work through the entire chain to find the bad cable! One would not initially suspect a cable because of the addition of a new component, which had been dropped/hit in shipping, introduced into the system.

In the end I am grateful that it was "just a cable" - the DAC, amp and all other equipment are fine. I happen to be deriving even more pleasure from the DAC than I had anticipated.

The Lesson for us all, and I reiterate for myself, is that we cannot make any assumptions when a problem arises. The testing has to be methodological. Even then, finding a cause can be tricky. One thing is for sure, I'm glad I didn't stop at concluding that the DAC was the cause. It would have been embarrassing to return a perfectly good DAC!

What are the odds that a cable would fail at the precise moment when a DAC is inserted into a rig? Or that the cable would work at low levels and cut out at high levels? Or that to diagnose at moderate levels I would not hear the woofers?
This diagnosis was a challenge! So, yes, I knew the odds of anyone guessing the correct problem was virtually nil. However, assuming that it was the DAC was incorrect. This problem would not easily have been found if I did not have an extra DAC and amp.(It could have been found, but how many of us honestly would have assumed it could NOT be a cable?) One of my points in this excercise is to reinforce that assumptions can mislead, and that one must think systematically (pardon pun) in diagnosing problems. So, forgive me if you felt I was teasing; it was meant only as a brain-teaser.

Next time there's an issue, I just may switch a cable FIRST!
Another reason to have a pair of headphones around. They can be quite handy diagnosing issues downstream. Congrats.
Many years ago, I had my stereo on, and when I tried to switch tracks on the CD player (using the remote) the lights in the room dimmed. When I turned the switch on the lamp, the stereo went off. Then I heard a strange clicking noise from the other end of the house, and found my computer making strange noises. Every time I flipped a switch, another area of the house would be affected. It took the electric company several hours to discover one leg of my power mains was loose in the junction box on the corner of my lot, so my house was only getting partial power. Every time I closed a switch, it would draw down the current somewhere else in the circuit.
Ok sparky, what was the issue with the cable itself? curious minds would like to know. thanks!
Bombaywalla, I didn't see any signs of damage on it, but I think it was a solder joint covered by the shrink wrap leading up to the spade. One cannot always tell just by looking.

Maybe it happened while I was handling them while eating fried chicken. ;)
you probably tapped/moved/bumped the cable while working on the unit. Or, maybe someone took an opportunity to clean back behind while you were tinkering.

Cable was already just got nudged along.

I give you credit for getting it. I just read this and that was my thought initial thought as well.

Tell tale sign of a short- you just went too far and guessed how it happened which is 1000 more impossible. My favorite response was that the bit rate on the dac was not selected properly. LOL. I guess anything is possible...

Thanks, Rob. My guess came from looking at the pic of his Amplifier - speaker cables look like they are rather close to each other....
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