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Loudspeaker noise from 300B
Loudspeaker noise from 300B
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Old 24th September 2007, 10:06 AM   #1
mavallarino is offline mavallarino  United States
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Default Loudspeaker noise from 300B

Hello to all,

I have a strange problem. I have already tried to search for this exact problem with little results.

There is a small speaker buzz arriving from both channels of my 2A3/300b amplifier.

There is no mains power to amplifier (and there is still this buzz).
The grounding looks okay (There wasn't this problem before).

No lights are present, no cellular telephones, WiFi is disconnected etc... No AC connected...

Is there a problem with the ouput transformers? How can I check without sophisticated equipment?

Please ask questions because it is difficult to write all important details. Thank you for your help.

Kind regards to all!
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Old 24th September 2007, 04:00 PM   #2
kevinkr is offline kevinkr  United States
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Location: Boston, Massachusetts
Loudspeaker noise from 300B
Try disconnecting the mains and all signal leads from the amplifier.

Next try disconnecting the speakers from the amplifier and shorting the speaker cables together at the amplifier. (No, I'm not kidding) If you still hear a buzz that indicates that you have a strong magnetic field in that area of your listening room. This indicates that your speaker wiring is acting as a loop (equivalent to a single turn on a transformer) and picking up induced voltages. Suspect nearby electrical appliances (fluorescent lights, big transformers used for low voltage lighting e.g quartz halogen lamps, hot water heater, high current mains wiring, etc..) I have run into this problem a few times over the years with highly efficient speaker systems.

If the pick up does turn out to be magnetic twisting the speaker cable conductors (making a twisted pair) should help.
"To argue with a person who has renounced the use of reason is like administering medicine to the dead." - Thomas Paine
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