It would be an interesting experiment.1. That the amp has been on the same amount of time in both cases ..
Easy enough. I light it up every day at the same time.2. Both sets of tubes are biased the same
.550 volts or so. I've yet to get them all exactly .550V. More like .549 to .551 but I don't think .002V one way or the other makes a lot of difference.3. That you use the thermometer on exactly the same spot on the amp or tubes...
That'll be a little tougher. The plate designs are a bit different. Would measuring the very top and maybe the bases be "consistent" enough? Which raises another question... Is the thermometer measuring the temperature of the plate in side the tube or the glass side?4. That the ambient temperature in your room is about the same ..
Pretty consistent here. 76 to 77 degrees all day.5. The location of the amp in the room is the same.
It never moves.6. Your playing music at about the same volume level in both cases.
Pretty consistent during the day. Typically around 75 to 80 dB. My speakers are VERY efficient (101dB/1w/1m) so the amp is NOT working hard at all. Well under 1 watt. Evenings after a beer or two I tend to crank things up a bit but rarely over 90dB. I doubt the amp ever sees more than 1 watt of output. I probably could have saved myself some $$ by buying a ST-70 kit.
As it is right now my "perception" is completely unscientific and based on nothing more than me holding my hand over the amp. On the other hand I am pretty sure that the amp is giving off less heat with the KT120s installed.
Now I just have to prove it.