Thoughts on Audio Research D70

@Hifigeek1: Never mind, the relcap 2.0uF bypassing the cathode (regulated B+) output of the regulator 6550C has deteriorated enough that when I paralleled in another 1uF all is good. Time to replace them bypass Relcaps too I guess.

Bypass with the same manufacturers caps as the coupling caps..

Point well taken, esp with coupling caps where I often choose not to parallel a tiny 0.01 for the sake of coherence. Would rather invest more and get a better single cap.

For B+ bypass my experience is YMMV. I noticed that blackgate lytics will sound hashy and smear if bypassed with a small film whereas others may benefit.

the D-115 B+s are all lytic + Rel2.0uF + Wonder 0.01 with regulated B+ to the screen rel2.0uF + wonder 0.01.
I also notice that the B+ to the 6922 gain stages have nothing at regulator (TIP41) output at all (!).

I think I am ready to move on to triode mode. Just realized the screen grid supply is actually the 6550 pass element's output. This will be useless if I convert to triode, kind of a waste.

Wonder why they use the solid state buffered regulated output for the small signal B+ and not directly from tube reg.

My guess is it's not quiet enough

Checked all the regulated B+s and they are quiet and stable. No more oscillations.
All diff amp balances measure AOK.
Gain is too high for my liking so in a sense it's indeed not quiet enough.
Maybe a triode mod will give me the extra benefit of lowering the gain.
The sonic signature is not lightweight and refined enough, lots of power though. I guess its what full pentode/tetrode mode is all about.