2. amps-preamps
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Help with hum

I have a hum coming through both speakers. It is independent of volume control and completely stops when the preamp is disconnected. Disconnecting source from preamp has no effect. I have tried switching cables and tubes from channel to channel but it keeps humming. I have tried all combinations of cheater plugs on both amps and on the preamp but with no improvement. Any advice regarding cause or diagnosis is appreciated. Preamp is Cary SLP-98 and amps are Manley Neoclassic 300b's.

Thanks in advance,

Dave
128x128dbrewer12345

Showing 1 response by jea48

jea48
4,266 posts
 
It is independent of volume control and completely stops when the preamp is disconnected.
Just a guess but I would bet the ground loop is caused by one of the amps. When you have both amps connected to the preamp the ground loop circuit is completed by the ics.....
Just for a test try hooking up only one amp at a time to the preamp. Check for hum.

Jensen makes an isolator that can be installed between the preamp and the amps.

http://www.jensen-transformers.com/

http://www.jensen-transformers.com/an/an004.pdf

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