kt-120 or kt-88?

It's not so much a power increase when swapping to 120s as a tonal difference...it's my understanding the 120s aren't taxed as much since they CAN handle more power than 88s, but there's no miracle power boost even though it might seem like there is. They often sound "larger." I like the sound of 120s in my amp, and they've lasted a long time (well over 3000 hours) with no audible signs of age.

I have been using the 120's since they first came out but my memory of the change from the 88's is that the 120's deliver more power and have more 88 magic than the 88's. Someone calls the 120's 88's on steroids. I kept a full set of 88's in case I wanted to go back but never even felt the need tp try them. Chris from the Parts ConXection told me that the 120's sound like realy good (expensive) 88's.
Denny

ARC switched most of its tube amps over to the KT-120 in November 2010. Previously, the 6550 "Winged C" was the tube de jure. My previous ARC amp was the VS-115, which came standard with the 6550Cs. I dropped in KT-120s a soon as ARC cleared the new tube.

At least as far as my VS-115 amp was concerned power output increased from 115 wpc to 128 wpc. Sonically, IMO, the KT-120s cleaned the floor with the 6550Cs. Better headroom, dynamics, bass, etc.

So there IS a power increase? Can I check that with my Radio Shack meter? Seriously...I have wondered if I could do that...I'd like to be able to say my amp is more powerful, but with proof!

You would need a 'scope, a signal generator, and an 8 ohm 'dummy' load to see the difference in RMS power output in ARC products...I have. A bit more power but doubtful it would be audible. The KT-120 is a better sounding output tube in ARC power amps designed to use that tube.