@tooblue
The Psvane tubes that I installed in the QS 120s had been broken in with other pieces of gear prior to being installed in the 120s. I find your response of uniqueness with the Psvanes with the KT150s very telling and accurate. I find they add a little meat on the bone if you will, a flavour I definitely favor...
When I first got the QS Mono 120s, they had a fairly linear presentation, top to bottom, nothing really stood out - as it should be (I guess). Coming from other amps like you have with Cary or Inspire, and previously using EL34s and KT88s too, I was expecting a tad more of the tube goodness. Swapping out the stock JJ and EI small tubes and rolling in some really good vintage small tubes showed what the amps could do, and how the larger KT150s would respond, favorably. Note: In the right amplifiers, with the right transformers, with proper plate voltage.
After trying several different vintage 12AU7, 12AT7s, the PSVANES were appealing to try and to see how close they were to vintage tubes. In the first few days they were a bit midrange forward and detailed. After 40+ hours started to notice characteristics similar to vintage and did not lose any bottom end. Midrange then dropped back a tad, perfectly in fact. They seemed to compliment the mono amps nicely, particularly for being new-production tubes. Much better than Russian re-issue tubes, in a different league for sure.
Today, the sound stage has recessed nicely, and the highs smoothed out a tad, and hopeful with another 20-40 hours will hear a bit more texture and velvety tones come through. With this added front-end tube tuning, liking the KT150s more. They pretty much repeat what you feed them on the front end, top to bottom. It’s the added tone/texture I was looking for. Closer now, not quite there yet. Hopefully with another 40hrs.
