Cliff Schecht wrote:My second attempt at the bucking box worked better than my first it seems. I used a bigger transformer and didn't hook up both sides of the 6V winding this time. Knocks the wall voltage down to about 120V and I finally was able to fire up my Rocket build. For some reason this amp was making me nervous, I guess the building process went too smoothly. But after all of the fuss about getting the voltages in spec, I flipped the amp on and it sounded awesome. The PPIMV I rigged up worked like a charm and everything was idling where I was expecting it to. I'm super excited to break this amp in during Christmas. I only heard it with "test" tubes but once I get a proper set of 84's and throw in some known good preamp tubes, it'll be a nice sounding amp for sure. I'll post some pics and soundclips in a thread when it's all buttoned up.
Cliff, what transformer did you use to drop your line voltage 8VAC?
I'd like to build a bucking transformer. My AC line voltage is getting too high,
I measured 128VAC today!
Would the drop in mains voltage be linear to the rest of the amp? In other words, if the mains drop 5%, will that result in the bias voltage dropping 5%? I spent almost 3 decades gigging constantly and i could write a book on amplifiers and how they would sound like crap one nite and great the next. Wasn't till i retired from gigging and built my 1st amp that i first had any thoughts about bias and mains voltage and wondered if that might often have been what was happening on some of those "am sounds like crap" nites. I always biased mine at home but i never measured the AC there. For all i know it may have been high as AC power goes and some gigs way low resulting in large differences. Just wondering how say a 10vac drop would translate as a change in a 40Ma bias voltage. If linear, IE:10%=10% then i don't think that would be bad enough to sound noticeably bad assuming they weren't already biased cold, which i never did.
