Thoughts on Audio Research D70

That's the one. Also make sure you measure 10 ohms at ground to common tap at output transformer.

all measured OK. Thanks HifiGeek1 for the pointers.

Took me 2 hours to carefully pull all the wondercaps and Relcap coupling caps out, and another 2 hours almost to install k40y9s into the amp (size and metal casing does NOT help at all).
The foggy when low volume and glare at high volume problem is mostly gone.
I get a lot more natural and airy sound with strings.
More to do but at least this IMO is going absolutely the right direction.

Here's an FYI. I own a D115MkII and called ARC about putting KT120's in the amp. They said don't do it as the heater in the KT120 draws alot more current than does the 6550s. He said that this will kill the power transfer over time. I would think that the D70 would also be in this camp.

I wouldn't put 8 kt120s into it. Consider how much more current the filaments will draw. 8 kt88s in tetrode mode should be able to power the hungriest of hogs. The apparent lack of power is from the stock caps. If you are not comfortable with DIY or non factory mods, ask Calvin at audio research if they offer recapping service for the coupling caps like they did i(infinicap and dynamicap) in the 90s. The relcap plus wonder cap combo is not conducive to good sound at all.

Sbrown, Thanks for sharing that info on the KT120's. I was wondering about this and was going to call Arc about it. You just saved me the call, LOL.
Too bad, as the KT120 is a very good tube. With decent 6550's getting a little hard to find, I'm glad I just re-tubed with SED's.