Thoughts on Audio Research D70

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.

Sbrown, I just replaced the 6550 in the power supply of my CD-8. ARC sold me a 6550 WE. No idea what it is, but if ARC sells it, I'm not worried.

@sbrown if you are just after the sound of the kt120 and not the marginal increase in power you can use just 4 tubes in your 115. That's how I sometimes run my old vt130 anyway. Make sure you are using one tube per phase per channel. Filament supply is parallel so you will never be stressing the unit with half the power tubes.