Arron had a couple of the 5150 heads and wanted to get more tone and a smoother compression from the amp.
The 5150, although sounding great, is a bit "hard" or harsh and does not compress very much - it also often has an unfixable bit of crossover distortion on the edge of notes.
So, after some counseling we got going on the project.
The first part of the job was to put in better power tubes. For the best compression and to still retain as much horse power as possible, we used the great Tesla-made Groove Tubes 6L6S.
This tube has a very heavy glass bulb, very large internal plates and a "soft vacuum" (the vacuum inside the tube is another component of the tubes sound, one that is ultra-important, but not discussed at all.) We used a very low number too, (2's)
But, this points out a serious problem with the 5150 - no bias control. No matter what anyone says, you need to set the bias on the power tubes!
Since the Tesla 6L6 is so different from the existing 6L6 tubes, the bias was now farther off than it was before!
The bias conversion is not too hard, just a bit puzzling to find all the parts.
After installing a bias pot and setting the bias to about 30 ma per tube, we were really getting some tone!!
The crossover distortion was gone, and there was more power, sweeter tone, and noticable compression of the notes.
Now the main part of the project. Adding a Torres Dual Rectifier kit, using two 5U4 rectifier tubes.
Torres Techs did all the work. carefully finding locations for the two tube sockets (in front of the power transformer) and the fairly large filament transformer.
The Torres kit includes detailed drawings of the Peavey rectifier and the wiring so this wasn't really hard. The only hard part was the locating of the tube sockets. There is precious little space (obviously peavey didn't plan on anyone adding two huge tubes)
Once this was all set up, the amp turned right on, and worked perfectly. The tubes were as tall as the power trans so they fit real well.
Now the amp had tone!! singing sustain, smooth compression on hard cords and notes, the hashness was gone, replaced with really great crunch, and a super punchy tone. No more crossover distortion, and the other complaint with 5150's was gone - the uneven tone. Now the amp was very responsive and dynamic. Certainly one of the best high gain commercial amps we have ever tried. Good project.