KT150 to KT120..or KT120 to KT150

@decooney, I purchased a set of Silver 88 mono-blocks back in 2014. When I ordered them, I paid extra for the KT150 customizations. I had always been running KT150s, but recently tried some KT120s. I am finding less high frequency extension with the KT120, and less midrange lusciousness as well. I run the KT150 at 50ma, and the KT120 at 44ma.  Maybe I have not given the KT120 long enough, but they came out of a friend's CAT amps, so I think they have been run for at least a couple hundred hours. I am curious as to what bias you are running the KT120s in your Quicksilver amps.

Thanks

@aljordan I now run between 45-50ma with the KT120s in the Mono 120 amplifiers. There is a difference, the Mono 120s have a plate voltage of 600v at the plate. Running the basic calculators, it says I’m barely close to running the KT120s in their optimum window. Don’t recall if Silver 88s run 450v at the plate or what.

Not near a place I can check but would be good to find out what plate voltage your amps are, and check a calc to see what is optimum current for yours, amps, tubes when running KT88 or KT120 or KT150. Yes, you’ll get less high freq extension with KT120s, part of what Iike about them in my setup. I prefer the midrange, and yet KT150s are totally neutral across the board in my amps biased at 45-50ma. Nothing really stands out with the KT150s I guess, maybe how it should be.

Different rooms, hearing, and preference matters too, along with speakers, cables, now I'm digressing, in circles. Haha.  

@decooney I just saw your follow-up a year and a half late. I did end up trying a different matched quad of KT120s in my Silver 88s, and they sound very good. 

@aljordan  Have you swapped back to KT150's to determine the difference between the tubes? I also wonder if the speaker that one uses has something to do with the results posted? Some less efficient speakers working better with the KT150's?