Post Phase Inverter Cathode Follower?

[bluescaster]

Hi, i add DCCF on my AB763 clone on paper. What do you think about it ?

Do you think U cathode-filament can be a problem ? how to fix it ?

Thank you.

[David Root]

That should work with the right component values. You might need a more negative raw bias. I have done this (not in Fender amp) using a separate power transformer providing 120VAC to the rectifier to get about minus 175V raw bias. I used a 12BZ7 not a 12BH7 though.

Take a look at this old Heathkit schematic. The bias is way more complex than you need but this how it was done in the '50s, with a 12BH7 and 6550s.