Help with Unbalanced Levels in an Alta Moda Hippo Stereo Compressor (500 Series)

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jjsound

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Feb 19, 2015
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Hey guys,

I just got a used Alta Moda Hippo compressor off of Reverb for a pretty good deal. Apart from some cosmetic issues, the unit was said to be fine. I plugged it into my 500 series chassis today and passed some signal through it. I ran an oscillator into it and checked to see if both sides were outputting the same level when it was in dual mono mode. It turns out that the right channel is outputting a full 2dB hotter than the left output when the unit is engaged and the threshold knob is fully CW, and as I turn it CCW, it the dB gab becomes even larger. Checking gain reduction, it seems that both sides are getting the same amount, at least according to the meters. The only thing that doesn't seem balanced are the output levels.

There isn't much info about this unit in terms of schematic. The manual basically gives you a sense of what the controls do and thats about it. I've emailed Alta Moda's "support" email, which seems to go directly to the guy who designed them, though he hasn't responded since I emailed him about 1 1/2 weeks ago.

There is a trimpot on each card that says BAL POT, which I did try to utilize, but it only changes the level about a 1/10th of a dB. It's a very fine trimpot it seems. Other than that, I don't see any other things on the PCB that deal with calibration.

This is a long shot, but do y'all have any idea how I might be able to fix this leveling issue?

Attached is the level of the unit 100% WET.
 

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jjsound

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Feb 19, 2015
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And here's a snapshot of the level when it's 100% DRY
 

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scott2000

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jjsound said:
There is a trimpot on each card that says BAL POT, which I did try to utilize, but it only changes the level about a 1/10th of a dB. It's a very fine trimpot it seems. Other than that, I don't see any other things on the PCB that deal with calibration.

Most likely that adjustment isn't for what you may be thinking and possibly may have made things goofier by messing with them....No biggie though..... can figure it out later I'm sure.....

Could be a number of things messing with your balance...... Maybe if there are dual gang pots in there, one side is not tracking the same....component going out of spec......etc

I guess chasing some voltages around the circuit would tell more of the story.......???

 

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