Stop in for a cup of coffee

I bought a variac on Ebay to bring up the AC voltage to my "new" vintage tube receiver. It popped my 20 amp circuit breaker upon plugging in a couple of times. I reset, checked the voltage out, it's smooth from 0 ish to 122 vac. At first I thought for sure it was the variac, there was some issue but after thinking about it, 1. It's fused itself, now maybe that's for the output but that fuse never blew, it's 2kv and 15 amp, old school heavy duty and it could be inrush current or noise and my new style circuit breaker won't tolerate the plug in. In use it will always be plugged in with the receiver plugged into it's outlet. Anyone have an opinion on this? Am I in denial?

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