I've found KT150s perform their best in amps truly designed to run them natively at their optimum operating rage.
My current mono KT150 amps run higher plate voltage, with 25% larger transformers, as compared to all of my prior amps with EL34, KT88, KT120s.
Tried KT150s in my smaller amps with lower plate voltage(s), and KT88s were better. KT150s sound different and better in the amps designed for them. It's a different sound, stage, tone, musicality in purpose built amps vs just plugging them into a socket that will fit them.
My current mono KT150 amps run higher plate voltage, with 25% larger transformers, as compared to all of my prior amps with EL34, KT88, KT120s.
Tried KT150s in my smaller amps with lower plate voltage(s), and KT88s were better. KT150s sound different and better in the amps designed for them. It's a different sound, stage, tone, musicality in purpose built amps vs just plugging them into a socket that will fit them.