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 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.

Smoffatt, probably not without modification. I believe that the bias pot range may be too small. If that is the case you would not be able to properly bias the tubes. You might need to changed the value of a few resistors. Not that big a deal. I had it done to a Classic 60 years ago. ARC sent me the proper resistors along with a schematic of where to replace than. There might also be clearance issues. The KT 120 tube is much larger than the 6550 tube. They may not clear the cages.