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Old 12th March 2004, 01:10 AM   #1
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Default Strange problem with amp

I have a strange problem with an amp. The casing is made of aluminum and steel plate. When I slap/hit the casing, it makes sound to the speaker (output). I check the electronic circuit, and it seems nothing is wrong. How can I fix this?
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Old 12th March 2004, 01:13 AM   #2
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Is it tube or solid state?
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Old 12th March 2004, 02:09 AM   #3
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It is solid state. The amp is monoblock. The left is ok, but the problem is with the right unit. I check the voltages, nothing is different, no other complain, just this strange casing noise. What I'm afraid that this is a begining of something worse, if it is not fixed immediately.
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Old 12th March 2004, 02:12 AM   #4
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My inclination would be to look for a cold solder joint or a loose connection.
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Old 12th March 2004, 02:14 AM   #5
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Patient: "Doctor, doctor, it hurts when I raise my arm over my head!"

Doctor: "Don't raise your arm over your head."

Capacitors are often microphonic. I doubt it's anything to worry about. And stop slapping your amplifier!
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Old 12th March 2004, 02:31 AM   #6
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One month ago both are fine. Why is it only occur to 1 amp? Is there a capacitor drying? I've check the connections they all OK, have to check for cold solder. Infact now, nothing is wrong with the sound, just makes me a bit worried.
Charles, I'm not intentionally slapping my amp. Just find it out unintentionally.
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Old 12th March 2004, 03:28 AM   #7
mwh-eng is offline mwh-eng  United States
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Quote:
Originally posted by Charles Hansen
Patient: "Doctor, doctor, it hurts when I raise my arm over my head!"

Doctor: "Don't raise your arm over your head."

Capacitors are often microphonic. I doubt it's anything to worry about. And stop slapping your amplifier!
Now that's funny! Maybe you heard that on the same old TV program, I heard it on. No, you couldn't be that old.

I agree that it's likely microphonics due to something physical. Modulating capacitor plates?
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Old 12th March 2004, 03:37 AM   #8
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I don't buy the microphonic solution. I still think it's just a bad connection.
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Old 12th March 2004, 03:52 AM   #9
mwh-eng is offline mwh-eng  United States
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Quote:
Originally posted by Bill Fitzpatrick
I don't buy the microphonic solution. I still think it's just a bad connection.
I believe you may have discovered a few cold solder joints before. I've found some, as well. Some that I caused and some the manufacturer left for me to fix. Depending on whether this amp is in a Lexus or 1 ton truck might give us a clue.

A bad solder joint would make a different sound than microphonics, don't you think? We need an MP3 sound file to listen. A cold solder joint would probably sound noisy and harsh. Maybe a microphonic sound would be more like high speed tremelo or vibrato effects.
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Old 12th March 2004, 01:03 PM   #10
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I've recheck the whole amp. Nothing seems to be loose or bad solder (they are dull, right?)
The sound semms like a slight "echo". When I slap the casing (sorry, Charles), it gives an echoed slap to the speaker. What is the cause?
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