I have a preamp I'm working on currently. I measure 1.2mV AC on the output of the supply which is feeding the plates of a 6CG7 SRPP circuit. I have ~6.1V on my cathodes & 300V on my plates.
On the output cathode side of my 6CG7 tubes, I measure about the same 1.2mV AC ripple. On the other side of the coupling cap, I'm getting 4X that or 3-5mV. Any ideas?
I've posted something like this before, but turned out it was in the power supply.
Thanks for any ideas!
Blair