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Slight hum from SLI-80 power amp

I own an SLI-80 Amp for a little over a year.  My system has developed a very low, slight hum only on the right channel. One has to get right up to the speaker to hear this hum, but it is still a hum that should not be there.
Any ideas where I should start looking to eliminate this hum?  Thanks
richfrank

Showing 3 responses by richfrank

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richfrank OP
34 posts
 
SFAR & JTCF: Received both of your suggestions and will follow your advise. Will report back later. Thanks.
richfrank's avatar
richfrank OP
34 posts
 
Swapped the tubes. The very slight hum stayed on the right channel.
I replaced the rectifier tubes with 5AR4's [had previously 5U4's] and readjusted the bias to 80 mA. No change. I did install in parallel a REL Acoustic sub-woofer system as per wiring instructions over ONE year ago with no problems. I wonder if there might be a grounding issue somewhere.  Very frustrating. I am totally baffled.
richfrank's avatar
richfrank OP
34 posts
 
JTCF: Have not swapped the speaker cables. This sound system has been working like this for over 1 year.  Why now this?  Your suggestion to remove all external connections like the sub-woofer and CD is a great idea. Your last sentence is very important. Thanks. I will try......

CDC2: I was told not to use a "cheater" to eliminate a possible ground loop,  but your suggestion (or should I say Kara Chaffee) sounds logical.
The sub-woofer is on another outlet since installation days over 1 year ago, but ......  I will follow your suggestion and advise......
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