Retubing an ARC VT100 mkll

Just a footnote comment about the KT-120s. I had about 3000 hours on my KT-120s and thought it might be a good idea to retube my amp. I bought a complete set of tubes from Upscale Audio and dropped them in. The price is about half what ARC would charge. Kevin Deal burns in his tubes for 72 hours before matching and then checks three electronic attribtes: bias, G2 and transconductance. After about 20 hours of break-in, it's quite obvious that the amp sounds better. FWIW.

Btw, one of the matched sets did not take a bias adjustment. I put an old tube back in and everything was ok. Called Kevin. He immediately shipped out a replacement matched tube. Everything is now good to go!!

Wow 3000 hrs. is well passed the recommended ARC replacement time. I would say you got lucky..

Gary, I'm sure you're right. But I wonder if the KT-120s are as susceptible to arcing or other malfunctions that would damage the amp as compared to the 6550 C tubes. The build quality impresses me that the KT-120 may have a longer life than 2000 hours.

I can tell you, they're still susceptible. If your amp was wired in triode, you might be able to get away with it.

Gary,

Is the ARC VS 115 wired in triode?? Regardless, thanks for the advice anyway. The 6H30 audio tubes were pushing between 4 and 5K hours too. So I retubed the whole VS 115 batch.

As an aside, I just ordered a retube set FROM ARC for my ARC Ref 5. There's probably over 3K hours on the 6550 C and 4 to 5K hours on the 6H30s.

Not sure what I did makes sense, i.e., buying VS 115 tubes from Upscale Audio and Ref 5 tubes from ARC. The thought process is that "ARC grade" matching might be more critical in the line stage than the amp. That's probably not a valid assumption, but it's a done deal. In any case, as stated, the KT-120s bias just fine and the amp sounds great, so I'll just have to "suffer" [sic] with the Upscale Audio tubes in the amp -- NOT.