Noise when changing the volume

If the noise is in both channels then you should look for something common to both channels. Capacitors are the likely cause, but some IC's might cause it. You say that the volume control doesn't effect it, if that is the pre-amp's volume control then the fault will be after that part.

A number if things can be wrong with it, from the audil preamp to the the audio amplifier. Even as simple as a bad volume control. Does the actual noise change patterns when you move the volume?

Guitar amps have preamp sections (think unpowered audio mixer) and power amp sections (Crown rack-mount amp). An excellent way to isolate audio problems if amp is still producing audio is to check the preamp out (line out). Preamp output distorted = preamp failure. Connect MP3 player to "Power Amp In"...sound distorted = power amp failure. In your case the latter is the case as your "line out" is clean. Also test each speaker for clear sound as speaker cone damage from being overpowered is fairly common. At 300w. I'll assume the failure was not from cranking the volume to loud but a shorted speaker or speaker wiring could zap the power amp in an instant.

This will be the large Electrolytic Capacitors in the Power Supply. You can't miss them. They will over 4700uf or around that in value. Replace them all, even if only one has gone. I think what your hearing is the 50/HZ hum from the mains getting in.

If the noise does not go away when you turn the volume control down the problem is in the output stage. If the noise is in one channel, then you should only look at that channel. Use the other good channel as a guide to what is working. If in both channels then it can only be something common to both channels. The bad news is that anything can cause noise.

Just look around the web for a "Magnetic Cartridge Preamp".
You plug your turntable into this and the preamp in an aux socket of Surround Amp and the sound will be the same level as the other devices.

Hi...

Is that the fancy pot with more than 6 leads..kinda square looking?

This place has some.

http://angela.com/

Rate my help if this helps...Thanks

I've never repaired one of these but I have an amp at home that makes a intermittent static "popping" noise that i'm going to put down to a dirty volume pot (control) that needs cleaning. I will also have to change some of the electro capacitors that have dried up inside which cause "shot noise". With the right lubricant (electrical contact cleaner, nothing else) you could take to lid off and spray a small 1 second blast into the hole of the pot and any other balance or tone control yourself but I would take it to the electronics repairer to get the capacitors checked over.
My theory only
Good Luck!

Hi

Sorry for the delay in getting back to you, you have an odd problem happening there, the pre-amp being the common denominator to the syptoms. Perhaps you could try reducing the attenuators to say 60% and retry at the same levels you used to use at the preamp. It is unlikely that there is a fault occurring that would increase the output of the preamp, more likely to be a DC component getting through. It could also be possible that the amps if all the same make and model have through over the period of installation developed the same fault.
There will have to be a common contributor to the symptoms. It is not uncommon for the same problem to affect a particular model at the same point of its life. Best approach and easiest to fault find it would be to change out the preamp with something similer to test the system and see what happens. At least tyouy will know where to start looking. Hope I have been able to help you, still happy to discuss it further. In the Free section our only reward is a FixYa ratings. Cheers

robotek

Check capacitors in power supply......also check for over-heated
resistors..all 1 ohm.....replace if cooked...................T.