I just tweaked the bias on the new KT-120s up a bit, to about 65/tube (1.3v on the meter) and indeed the sound opens up quite a bit at both ends. Wonder what this would to to tube life?
2 posters
Against my religion, but . . .
deepee99- Posts : 2244
Join date : 2012-05-23
Location : Wallace, Idaho
Bob Latino- Admin
- Posts : 3262
Join date : 2008-11-26
Location : Massachusetts
The higher you bias the amp, the longer the M-125 amp stays in Class A before switching over to class AB1. This does have a subtle effect on the sound of the amp - usually for the better - BUT - as you well know > the higher the bias the shorter the tube life and the higher the bias the more current the amp uses and the more heat the amp produces. I have run the bias on my own M-125's up to 75 milliamps per tube. The amps ran noticeably hotter and sounded fine - BUT - I do not recommend doing this. It puts a strain on the power transformer and the rectifier has to work harder also.
Bob
Bob
deepee99- Posts : 2244
Join date : 2012-05-23
Location : Wallace, Idaho
Bob Latino wrote:The higher you bias the amp, the longer the M-125 amp stays in Class A before switching over to class AB1. This does have a subtle effect on the sound of the amp - usually for the better - BUT - as you well know > the higher the bias the shorter the tube life and the higher the bias the more current the amp uses and the more heat the amp produces. I have run the bias on my own M-125's up to 75 milliamps per tube. The amps ran noticeably hotter and sounded fine - BUT - I do not recommend doing this. It puts a strain on the power transformer and the rectifier has to work harder also.
Bob
Well, I'll try .65 for awhile, see if it's worth it. I just checked the xformers and they're warm to the touch but not hot, about the same as .6.
I believe I read that sKiZo runs his at about two volts, but then again, we haven't heard from him for a while. Perhaps there is a smoking black hole. This would not be good.