Thoughts on Audio Research D70


I recently saw a very well priced D70. If I remember back in 80's these were highly thought of. Having no chance to hear, what do they compare with today or do they?
128x128daveyf
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.
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.
You realize you will only get about 35-40Wrms across 8 ohms in triode configuration...