Anybody tried KT120 tubes on Conrad Johnson amps?

Sparky, not to sound argumentative; but I do not think that upgrading the caps in an amp is the same as swapping a non-spec'd power tube. Capacitor technology has improved significantly in the last 30 years, and there is little to no risk in replacing old caps with new ones of the same (or compatible) values. But that's not the same as a power tube substitution, which in many cases compromises the integrity of the system design.

I'm not implying that it should never be done, but in my book it's an all bets are off decision. I'm not interested in being an unpaid beta site with my good tube gear.

Br3098 I totally agree with you. Caps can make a huge difference and not all caps work well as coupling caps. There are caps I would use for crossovers that I would never use for coupling caps and vice versa. The bottom line is: all these tweeks, be it caps, or tubes, or speaker wire and interconnect cables are tone controls. Shaping the sound to the room and your taste.

I also want to upgrade my amplifers. I want to upgrade the capacitors, resistors and wiring. CJ announced they have capacitor upgrade C1 for old amplifiers. They ask 2000 Dollars for each amp. I think I will go for Mundorf caps. I used to have Unison Research S8 amp, I modified it with Mundorf caps, Japanese tantalum resistors, good wires and DACT attenuator. All this mods took the amp to another level. But it took about 300 hours for breaking-in, wich drowe me crazy.

HI Guy's
I totally agree. A cap upgrade is pretty safe and I believe I indicated that. I just wanted to not discourage folks from certain kinds of upgrades that are safe and can really add to the sonic experience. Tubes are a different story and should be done very carefully.

My guess is I will never upgrade to the KT120. The differences with just the heater current, while not great for a single tube, adds up when you consider that I have 16 6550's not counteng the regulators. The resulting added current may well overload the heater supply. I'm very curious about others experiences.

Sparky

Karma if you want to upgrade your amp replace all the electrolytic caps in the amp if you haven't already. That will make a huge difference especially if that amp has the old style twist lock lytics on the high voltage side. ARC's upgraded caps have an adapter on them. They are not twist locks but with the adapter plate they provide it's a drop in replacement. Twist locks have high ESR. When I upgrade an ARC amp I always replace them. Also I don't have a circuit diagram in front of me but if you own the MKII servo and your so inclined I would find a better ic for the servo. Put in an IC socket so you can easily remove them. Servos IC's do have a sonic impact. Servos were a good idea at the time, but they're not really used all that much anymore.