Strange problem with amp

lumanauw · 12th March 2004, 12:10 AM

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?

Bill Fitzpatrick · 12th March 2004, 12:13 AM

Is it tube or solid state?

lumanauw · 12th March 2004, 01:09 AM

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.

Bill Fitzpatrick · 12th March 2004, 01:12 AM

My inclination would be to look for a cold solder joint or a loose connection.

Charles Hansen · 12th March 2004, 01:14 AM

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!

lumanauw · 12th March 2004, 01:31 AM

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.

mwh-eng · 12th March 2004, 02:28 AM

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?

Bill Fitzpatrick · 12th March 2004, 02:37 AM

I don't buy the microphonic solution. I still think it's just a bad connection.

mwh-eng · 12th March 2004, 02:52 AM

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.

lumanauw · 12th March 2004, 12:03 PM

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?

12th March 2004, 12:10 AM	#1
lumanauw diyAudio Moderator Emeritus Join Date: Oct 2002 Location: Bandung	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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12th March 2004, 12:13 AM	#2
Bill Fitzpatrick diyAudio Member Join Date: Jun 2001 Location: Eugene, OR	Is it tube or solid state?

12th March 2004, 01:09 AM	#3
lumanauw diyAudio Moderator Emeritus Join Date: Oct 2002 Location: Bandung	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.

12th March 2004, 01:12 AM	#4
Bill Fitzpatrick diyAudio Member Join Date: Jun 2001 Location: Eugene, OR	My inclination would be to look for a cold solder joint or a loose connection.

12th March 2004, 01:14 AM	#5
Charles Hansen diyAudio Member Join Date: May 2003 Location: Colorado	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!

12th March 2004, 01:31 AM	#6
lumanauw diyAudio Moderator Emeritus Join Date: Oct 2002 Location: Bandung	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.

12th March 2004, 02:37 AM	#8
Bill Fitzpatrick diyAudio Member Join Date: Jun 2001 Location: Eugene, OR	I don't buy the microphonic solution. I still think it's just a bad connection.

12th March 2004, 12:03 PM	#10
lumanauw diyAudio Moderator Emeritus Join Date: Oct 2002 Location: Bandung	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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