V4B - Dual Bias Control - External Set Up

[Roman Ships]

It really depends on the kind of precision you want. I tend to think that 4 bias monitor ports is a bit much, but if your tubes are super mismatched it may be worth your trouble.

if you want to have independent bias control of each half you could just have two bias pots where R75 is, and have the output of each go to a different side.

or you could follow the silver face fender style of balancing the power amp instead of biasing.

alternately you could combine the two. what do you want to do?

Here is my opinion: I don't think most of this is particularly necessary. Ampeg biases these amps pretty cold (around 60% max plate dissipation), and they actually sound good that way. I have tried biasing them hotter, but they get pretty muddy and lose definition.

personally, Ive stopped installing bias pots in V4s because they seem happy without them, and installing them and boosting the bias doesn't make them sound better. (as it would on a mesa boogie or silver face fender)

My interest really isn't increasing bias, I just want to know that it is in a good range and I want to be able to do so without opening the amp... plus its a fun project.

It has been too mushy for awhile in my opinion. Perhaps I should wait until I have the rest of the issue figured out and then assess whether I should install a bias control.

Clarification: You said R75, I don't believe there is one. Did you mean the 75k resistor I wanted to put in?


Also, I took out the hum pot and was going to tie 100 ohm resistors from each heater to ground. I read this was a good alternative.
That sound ok?


thanks,