My Soldano HR100+ head is rated from the factory to run at 234 volts from the mains line. Here in my country we have a mains voltage of 220 volts...so I'm running the amp at -14 volts of its intended voltage. I recently rebiased the amp, and when I measured the plate voltages I got 447 volts. Bill Sundt of Soldano has just emailed me telling this amp's plate voltage is 500 volts when running at the rated mains voltage. As you can see, I have a problem here...I need some extra 50 volts on the plates to have the amp sounding just like Soldano designed it. I told Mr. Sundt I had just rebiased the amp at 30ma. on the 5881 tubes, and his reply: "30 mv should be fine. We actually set the amp cold at the factory, at about 20 - 25 ma, but that is with the plate voltage at 500 volts. The lower mains voltage you have there is reducing the current in your amp and increasing it should help." I guess I could use a variac...but that's too clumsy since I tour with this amp. Is there any other solution you guys could think of? Thanks!