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Weird Compressor Issue - Any Ideas?

jtwiddler76

jtwiddler76

Active Member
Hey y'all,

I picked up a PreSonus ACP88 8 channel compressor/gate off craigslist recently and for the most part, it works fine. Unfortunately, two of the channels have a strange issue and I'm not sure where to start the diagnosis.

This thing is no longer repairable by PreSonus so I'm on my own. Here's the issue.

When I use these two channels with the issue, they work fine for a while, but after 5-10 minutes of use, the audio volume drops and begins to distort. If I keep trying to use it (running guitar or vocals through it) it's quiet. But if I don't run any signal through it, it comes back in a few minutes and sounds fine.

The odd thing is this happens even when the unit is bypassed. I did hook up a couple of the channels wrong (I put the tip and ring cables in reverse) when I first got the thing, but I don't remember if it was those two channels or not. So I don't know if it could be related to it or not. I'm running all 8 channels as inserts into an 8 channel mixer that takes a TRS cable. I've got an 8 channel snake with TRS on one side, and two Tip and Ring cables on the other.

Thanks for any ideas.
 
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Do you have a way to trace the signal inside the unit?

Having other channels that work fine will help you to trace the signal. I'd feed 1KHz to one bad channel and 2KHz to one good channel so you can spot which signal you are seeing or listening.

If you shorted a balanced output to ground, that could damage something, so I'd start tracing backwards, from the output jacks.

If the unit received some high voltage at the input, the input amplifier could be damaged. In that case tracing from the input makes more sense.

I've traced signals even with my DMM, feeding a 50 or 100Hz sinewave to the unit under test.
 
Last edited:
elnaldo said:
Do you have a way to trace the signal inside the unit?

Having other channels that work fine will help you to trace the signal. I'd feed 1KHz to one bad channel and 2KHz to one good channel so you can spot which signal you are seeing or listening.

If you shorted a balanced output to ground, that could damage something, so I'd start tracing backwards, from the output jacks.

If the unit received some high voltage at the input, the input amplifier could be damaged. In that case tracing from the input makes more sense.

I've traced signals even with my DMM, feeding a 50 or 100Hz sinewave to the unit under test.
Click to expand...

Thanks for the ideas, hrmm. I have a multimeter but it doesn't do tone generation.
 
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