Rolling KT150s in Primaluna hp integrated

"The sound is to die for", different amp(s), same result, Jbhiller, I agree. The KT-150 tube is the difference. Temperature effect would depend on many factors, room size, amps, local, season, etc not withstanding George's technical considerations. 
 

In my case it very well may be that there was more miles on my original KT150s than I realized and that putting in fresh tubes made the difference and it had nothing to do with the cryogenic process.

The way to test this, is to send your healthy original used tubes away for cryo'ing (make make sure you get the same ones back by marking them). Then having a listen to them again.

Cheers George    

@georgehifi  PrimaLuna emphasizes that they run their tubes about 1/2 -2/3 as hard as other manufacturers in order to NOT overrun the tubes, especially since PL encourages listeners to tube roll with expensive NOS tubes. I believe the amp also gets a more stable load and presumably lower distortion with not running the tubes so hard and hot. 

@a25105 In the Sta Cruz Mtns, gets up to the high 90s and tops 100' as well. problem is, I live in an old barn converted into a home with cinder blocks under the wood siding. Absorbs heat like a mo-fo. No AC. I would come home from work and not be able to listen to my system! And no plans to move soon.
But the heat from the PL Integrated is from the tubes and the 3 Large Transformers hiding in the back under the metal cover .... 

1graber2
@georgehifi PrimaLuna emphasizes that they run their tubes about 1/2 -2/3 as hard as other manufacturers in order to NOT overrun the tubes, especially since PL encourages listeners to tube roll with expensive NOS tubes. I believe the amp also gets a more stable load and presumably lower distortion with not running the tubes so hard and hot.

Grabber, "running a tube hard or not" is just the bias setting for the tube. It has nothing to do with the heater/filament current which is the main producer of heat that comes from a tube amp.

Cheers George

Great idea George! I didn't think of that. Comparing test results through a Hickcock tube tester probably won't tell me all I need to know with regard to the effects of cryoing the original tubes and comparing directly.