audio Research REF 110 and KT 120 tubes

I would also be interested in how they sound in the REF 110. I think that one of the reasons ARC changed tubes is the availability of the SED "C" 6550s. I have heard that the SED "C" 6550s may no longer be in production.

I also read somewhere that replacing the 6550`s with the KT 120`s upped the power by 20 watts per side. Or maybe 20 watts total. Can anyone confirm that?

I was told by ARC that not only was the KT 120 a better sounding tube. That it would increase the power of the Ref 110 to approx 130 wpc. The KT 120 is a drop in replacement in the Ref 110.

Lostbears...ARC told me the same thing. They also said that since they are drop in replacements (i.e., no change in bias settings from when the 6550s are in the circuit), they are being run much more conservatively at the existing bias settings so that the tubes should last longer and theoretically they are expecting less in the way of tube failures. I recently had my Ref 110 retubed by ARC with 6550s so I will probably just wait before retubing again with the KT120s.

I am due for new tubes in my Classic 120's. Wonder if the KT120 would be a drop in as well. It seems that the SED 6550C Winged are really getting scarce. Not too many tube sellers have them anymore and i would need 2 sets of matched Octets. I will call ARC and find out.