New KT150 tubes?

Ok. I have similar concern.
Have an aplifier designed to work with 6550/KT88 family of tubes.
Now I have KT120 installed - ok by manufacturer.

I was considering using KT150 im my amplifier, but manufacturer adviced not to do so. The point is not that both KT120 and KT150 have almost the same current draw. The point is different characteristics (curves) in KT150.
When used in amplifier with plate voltage lets say - 485 V and fixed bias point using KT150 will lead to use the tube in non optimal characteristic point (not the most linear part of characteristic). This is at least explanation I got from amplifier manufacturer.

Using KT150 in their optimum requires output transformer to be specially wound for them as well as setting proper working plate voltages.

Milimetr ... that's a great explanation. I'm sure the factors you describe are (or were) also under consideration by ARC.

Quite honestly, I'm not sure what "life testing" entails. Perhaps it involves running the tube in actual operation in the amp to check if it has a deleterious effect on other components. It might involve long term subjective sonic testing. Not really sure.

That's why although I am personally interested in following the outcome of ARC's testing process, I'm not so curious to plop those tubes into my ARC until ARC gives the green light.

It's all a bit like waiting for the college of Cardinals to elect a new Pope. Perhaps there should be a chimney in Minesota, so we can all wait outside for the puff of white or black smoke.

David12, better that than a puff of white or black smoke from your amp. ;^)

What if Putin decides to get back at the "West" by cutting off the supply of KT150s? What will audiophiles do then? 8^)