New KT150 tubes?

I too waited anxiously for ARC to bless the KT150 s with the Ref 150 when I reached 2,000 hours on my KT120s in the summer. But they didn't, so I purchased another set of ARC KT120s.
I have owned 2 ARC amps and 3 preamps and have always purchased my tubes directly form ARC due to the comfort factor, but the reports were so good on the KT150, that I managed to meet with an insider at ARC who assured me that, unofficially, the KT150s were recommended for the Ref 150. Purchased a matched set from Upscale and can say they are better than the KT120s. Just sorry I didn't take that shot earlier cause I now have a full matched set of KT120s with only 500 hours on them.
Go with the KT150s. You won't regret it.

Bifwynne, I was a big ARC fans too. My first hifi preamp was ARC LS-1 in the 80's. I had used the 40th Anniversary and recently upgraded to Ref 10.

I brought a pair of Reference 250 last year and in the first week, one of them failed to power on after shut down. They were finally replaced. My recent experience with ARC have been fairly bad. Reliability is a real issue.

ARC had lost my support on power amp. My amp had been changed to Pass Labs and to me Pass Labs sounds better. It is kind sad to see ARC losing its long time customers.

I've been running four KT-150 in my VSi75 for about a month. At first I was enthusiastic. The sound has more power and more depth as somebody else already said. But, it sounds a little less "sophisticated". It sounds great, but has less finesse. Maybe that's the difference between something that is specifically designed around a specific tube. Anyway, if you like more power in the most basic meaning of the word, this is it. What a bargain upgrade.

PS: What I meant to say is that to me the KT150s sound much better. Out of curiosity (audiophilia nervosa) I plugged the KT120 back in a few times and even tried to mix both types of tubes but I always quickly returned to just using the KT150s.

Just found this on another site.

ARC amps and KT150's

Audio Research finally clarified this morning in writing that the KT150's are electrically compatible with the following:

VSi60
VSi75
REF75
REF150
REF250
REF750

However, because the KT150 is physically larger than the KT120, technical compatibility has not been confirmed at this time. For example, they indicated there might be a "clearance problem" with the top cover of the REF75. MEP can you confirm?

There should not be an issue with the REF150 or REF250.

They made mention that the proper selection of the bias range and device matching of the KT150 tubes for each model is of critical importance for optimal sonic performance. They recommended customers purchase properly matched and biased KT150's from Audio Research for their particular product - when they become available from ARC - later in the first quarter.

They mentioned that KT150 tube sets will not be available for the REF750's for quite a while due to the tube matching requirements for a pair of the big 750's.

ARC made mention that they will NOT be held responsible for damages and/or repairs to a product if the KT150 tubes were installed that were NOT purchased as a set from Audio Research. Interesting.

No mention of pricing