@atmasphere I think you are right about the KT150. + @daveyf + @fsonicsmith1
Yes, I have been tracking both KT150s and KT120s past 3 years, closely. Picked up two spare quad sets in small availability windows that came and went again. My amps use these tubes only. Checking monthly, the group of less known suppliers I use [who stock up] are out of stock, again. Checking the manufacturer - they are out of stock again too. Clearly the war and supply lines as mentioned is not helping the situation. The major supply in volume outside of individual sellers is relatively thin, gone for now. The supplies I tracked that "were coming in May" are "out of stock" again or never came in. Not sure exactly but the message is the same.
Following ARC past few years, they were purchasing big batches, and then sorting again matching even closer matched sets in supply box groupings/ranges for new amps and replacements for customers re-tubuing their amps.
Seems It's kinda hard to sell new amps or service existing customers in volume when you can't get output tubes in supply, or how you need them. I'm wondering who will surface to clone KT120s and KT150s, take it on, and start selling them.