WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
I bought a Variac from FleaBay that allows me to adjust the voltage going to my amp. I got it for testing, but you could just leave it on. I assume there are 220 volt versions of them as well. Mine was about $50 for a 500VA unit with a meter.
