New KT150 tubes?

Xumbug .... as a general matter, I would be remiss to advise fellow ARC owners to drop KT-150s into their amps unless ARC said it was ok. Much of the discussion in this thread pertains to dropping KT-150s into current vintage ARC Ref amps, namely the Ref 75, 150 and 250. These amps were specifically designed to handle the KT-120s. The design changes included a beefed up power transformer and power supply.

Admittedly the predecessor Ref amps (namely the Ref 110 and 210) are able to handle the KT-120s. However, as reluctant as I would be to drop the KT-150s into the current Ref amps (such as my Ref 150) until ARC sprinkles pixie dust on the tube, I would be even more circumspect about the earlier version Ref amps.

My thought process is that these earlier amps may not have sufficient power supply head room to handle the additional demands of the KT-150s. And that doesn't even speak to whether the KT-150s are compatible with the older circuit designs.

Just my humble opinion.

I get that you are ready for new tubes since you have 2300 hours on your KT-120s. And those pups are ripe to the point of rotten. I sure wish ARC would fish or cut bait already.

And since poor Kal and Chris at ARC have been pummeled with a million calls about the KT-150s, I'm afraid they will confiscate my amp if they suspect I directed anyone else call them. LOL :)

Regarding which of the ARC Reference amps would be most likely to accomodate the KT150, I did get some advice from a dealer in ARC about 9 months ago. The advice was the fewer the number of output tubes, the less likely there was to be a compatabilty problem. This means of course, that the Ref 75 I have, was the best candidate. This was NOT a go ahead to try it though.

Hi Bifwynne, Thanks for the response! I will be a little more patient then and will wait another month or two and hopefully someone will have more definite answers for me. It will be great if the 150's can be used!

Chances are that the 120 to 150 swap is not as big an issue with the ARC amps designed for the 120s as going to 120s in an amp originally designed for the 6550. The issue in my mind is the QA done by ARC on the tubes they sell and warranty. Putting 150s in w/o ARCs blessing imparts two risk factors, one that the circuitry will not handle the tube and two, that tube variation may contribute to failures due to potential incompatibility. It's all about how the individual accepts the risk/benefit ratio. On buying a used amp I would send it back to ARC for a tune up unless it was essentially new. Did that w/ my VT200 even though it was a pain.

07-04-14: Xumbug
I have a pair of Ref 210 that have been upgraded to the KT120 with full resistor replacement by AR. My problem is: The tubes now have 2300hrs on them and I might need to swop them out. Do you think I can put the KT150 in them?
Xumbug (Answers | This Thread)

Yes, Go for it!