KT120 tubes in AudioResearch ref 300 MK2


I own the ARC ref 300mk2 mono-amps and i wonder if someone have any experience with replacing the powertubes for the Tungsol KT120.

More specific: Is there enough room because the KT 120 is a bit bigger?
Does it gives problem with the heat?
Is it necessary to replace the filament-transformer,
because the Tungsol needs more current?

What is the soundexperience?

Beersum, I own an ARC VS-115 amp and replaced the 6550 "Winged C" tubers with KT-120s. IMO, the KT-120 are a better tube: more head room, better and tighter bass; just better!

Here's the rub. Not all ARC amps are set up to take the switch. Call Calvin at ARC before doing the switch.
Please note that I have never found a single reported case of KT120s overheating any transformer anywhere ever at any time in the history of the universe....and I've asked around. I'm using 'em in a Jolida amp and they sound killer compared to the fine stock 6550s and an also great sounding set of Sovtek KT88s. I just love them 120s!
Hi Bifwyne,

Thanks for your advice, i have had contact with ARC, they already told me not to do.

The reasons:
The filament-transformer is not powerfull enough.
There will not be enough space for de KT120.
The KT 120 is to heavy for the socket.
That's a shame, but better you asked first. If you ever change out the Ref 300 mkII for another ARC Ref amp, e.g., the new Ref 250, the KT-120s come standard. In any case, I'm sure the Ref 300 sounds great. I hope you continue to enjoy it for years to come.
The best thing you can do for those amps is turn them into CL-150's. Triode connect the outputs. It will sound better and make it more reliable.