My Welborne-mod ST70 sounds fantastic, but a few months ago, I noticed annoying audible buzzing from both channels. The noise could possibly be related to Plug-N-Power devices which were installed throughout the house. These are essentially lamp dimmer and switch/relay modules that plug into outlets and are controlled through the household wiring by a remote controller (also plugged into a wall outlet). I am using a high quality shielded/teflon power cable. The noise sounds higher pitched than 60 Hz. Could the Plug-N-Power modules be sending audioband harmonics into my amp, or should I be look to faulty circuitry for the problem? All tubes have been swapped and the noise continues. Would a Gatekeeper restore a blacker background, or should I ditch the Plug-N-Power devices?
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