My tube amp causes isolation transformer to buzz


So I have an ARC Classic 60 tube amp that was causing a hum/buzz on my speakers regardless of volume.  In an effort to eliminate variables I plugged the amp into a Variac Transformer.  The sound from the speakers was almost completely eliminated, however once the power was turned on at the amp the transformer, which was otherwise silent, started to buzz.  Not super loud but audibly.  My amp draws 350 watts at idle. My Variac can handle up to 800 watts. 
So my question is, does applying a load to a transformer cause it to buzz, or can the amp cause the transformer to buzz?
last_lemming

Showing 2 responses by noromance

Oh, and a variac isn't an "isolation transformer," it's an autoformer where the pickup wiper is on the same coil.
It's buzzing under the relatively heavy load as the coil is energized by the alternating current. You could try the ubiquitous  red $110 20A 2000watt model.