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P88 sound leakage
P88 sound leakage
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Old 27th January 2010, 01:31 PM   #1
ivant is offline ivant  Singapore
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Join Date: Mar 2009
Default P88 sound leakage

I've assembled a preamp based on the ESP p88 and ran into some problems. Somehow with the volume knob turned all the way down, i still get some output at the speakers. Its soft but I can still hear it if i put my ear near the speakers.
Click the image to open in full size.
The board is configured as above.
I tried shorting the input of the 2nd stage opamp to ground and its still the same.

Could the problem be due to insufficient power supply bypassing? Currently there is only a 100pF ceramic cap across the +ve and -ve pin.
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Old 28th January 2010, 04:37 PM   #2
east electronics is offline east electronics  Greece
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Join Date: Jan 2006
Location: Athens GREECE
it could be a grounf or harware issue

by turing ccw on the pot the wipper touches the ground so input pin of your ic is shorted to ground there should be no sound at all coming from output

/so it can be a leacky or faulty pot
/it can be that the ground is no real ground and its floating by some hardware issue
/also it can be so that your construction and wiring is wrong and the output ic is "picking up " things on the way

post a photo of your construction and double check everything for mistakes
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