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BAT VK75SE buzz and humming ?? help..

Hello all, received a BAT VK-75SE which by the way is a lovely Tube amp for those that are not aware.

Unfortunatly I have plugged it in and have had a constant buzz since day one.. the buzzing remains even when Interconnects are removed and ground is lifted

I have :

1. Plugged the amp in a different part of the house- No Change

2. Changed Speakers and speaker cable - No Change
3. Changed PowerCord and Lifted ground - No Change

The amp itself is dead quiet, no transformer hum or anything.. could tubes do this ? ..

thanks all in advance !

Matt
mzn50

Showing 2 responses by marakanetz

marakanetz's avatar
marakanetz
5,473 posts
 
You can test your amp by light touching of chassis arround the input tubes with screwdriver and hear if buzz increases or you hear pops. You can also bring close light bulb. Normally BAT units will not react on light bulb brought close to amplifier but if there is a bad tube they will oscillate. That will definitely indicate that tubes need to be replaced not neccessarily input ones but any of existing.
If it won't help you'd have to get in touch with BAT and probably send your unit for service.
marakanetz's avatar
marakanetz
5,473 posts
 
What tubes and how old is the amp?
I assume that VK75 is not a long time in production to undergo capacitor replacements for instance. The fact is that if it "eats" tubes especially one earlier than others than definitely something is wrong.
You may want to check bias if possible. Tube oscilates when it doesn't have negative-enough grid voltage. Check an output tube manual for allowed negative voltage tolerance or call Viktor to find out and measure between the ground binding post and pin#5 with amp on and no tubes using voltmeter set to measure low-hundreds of volts.
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