Adjustable Bias schematic?

[hubb_99]

i am thinking about modding my dual rectifier 3 ch. head with an adjustable bias. has anyone seen any schematics floating around describing this mod.

 

[ylo]

I suspect you will have to come up with your own. You need a voltage divider using a pot with the right range, something like -40 V to - 65 V (roughly). You may want one for each tube, or one for each pair, your choice. You will want to look at the layout, not just the schematic. You will want to figure out where to put the pot(s) with the minimum amount of hacking to the amp. You want to do a neat, reliable job, and make it easy to reverse if necessary.