KT120 Vacuum Tube from Tung-Sol

[E-Stat]

I have yet to try an amplifier that is actually designed for KT120's...

Indeed. Changing tubes can alter the voicing. While you are pleased with the result, I would not swap the 6550s in my VTL amps for KT-88s as they sound "tubish" in them. Yet KT-88s sound neutral in the McIntosh 2301s. Audio Research just announced the REF 150 which is designed from the outset around the KT-120s. Ironically, the tubes are less expensive than the SED 6550Cs used in my MB-450s. It would be interesting to try them out, but it would be a costly experiment since I need eight pairs.

rw

[Raj J]

Indeed. Changing tubes can alter the voicing. While you are pleased with the result, I would not swap the 6550s in my VTL amps for KT-88s as they sound "tubish" in them. Yet KT-88s sound neutral in the McIntosh 2301s. Audio Research just announced the REF 150 which is designed from the outset around the KT-120s. Ironically, the tubes are less expensive than the SED 6550Cs used in my MB-450s. It would be interesting to try them out, but it would be a costly experiment since I need eight pairs.

rw

Yes, you would require 8 pairs; I did the same thing when I had those massive Manley reference 350 monoblocks from VTL. They previously had 6550's and I did a complete tube replacement with KT90's. The change was well worth it! I was driving maggies and Infinities thereafter, the KT90's did a fantastic job!

Don't get me wrong the 6550c is an excellent tube, infact conrad johnson and Audio Research swear by it, hence it's being around for decades...
But this KT120 is a very special tube indeed. I don't know what exactly it does and I had my doubts about using it at first since I have always trusted & used 6550's. I guess it's also to do with the circuit, if it is simple and can handle the properties of the KT120 then I would think it would work fine. It is not like a KT88 or any of the other KT series. It is way beyond any of those put together. What I get is a mix of EL34 magic, KT90 power and 6550 finesse all in one. My c-j power amp (MV60se) is only rated at 60 watts, now with the KT120's performs more like a 120 watter! I also think a lot of it has to do with the c-j ACT2 preamp. It matches extremely well with the power amp and drives the Quads effortlessly to full live scale levels. Again it's all do to with synergy and component matching.

Therefore I guess you would have to carefully match your tubes before trying anything out. You would also have to turn down the bias before installing just to be on the safe side. But one thing I do know is that my Manley 350's worked very fine with KT90's, so KT120's should work as well and even better! It is an adventure afterall...
I am sure your VTL's will deliver a performance that you have not yet experienced.
Ask Luke and see what he has to say...

Cheers, RJ

[E-Stat]

I also think a lot of it has to do with the c-j ACT2 preamp. It matches extremely well with the power amp...

That is exactly my concern. Since my system doesn't require a line stage, there is no need for me to change the voicing of the output tubes to match another component's personality.

rw