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My amp is a KT88 based integrated which uses 4 tubes in the final in a push-pull-pull configuration. Since I have owned it the power transformer has always run hot to the touch after several hours of use. Hot that you would not want to leave your hand on it for more than 10 seconds. Will not burn you but too hot to want to hold onto for any length of time.After searching the forum here I was led to believe this is normal and not to worry.
Today I switched out the four output tubes from EHKT88 to a new set of JJKT88. For whatever reason the transformer now is running cool in comparison, a very noticeable difference.
Is this the nature of the beast in that differing tubes can have that much of an impact on heat generated?
The amp is self biasing if this shed any light on the question.
If this is to be expected they I’m a happy camper since the JJ’s sound one heck of a lot better (more low end slam).
Thanks for any insight.
Follow Ups:
The bias may have been set too high or you need to rebias the tubes in the unit as they will bias a bit different than the previous tubes. How does it sound?ja in clear and cool this AM, Tucson, AZ
The Elaborate DAC=55/76 or 27 Balanced Preamp=Balanced Six Pacs=Newform Research 645
Your new tubes are drawing less current, thus causing your transformer to run cooler. I am sure, if you wanted to, you could increase the idel current and get the transformers hot again.
So I guess I will have to live with the cooler transformer. My only concern would be is the cooler condition a bad thing?Sound wise the amp is just fine. In fact the JJKT88's sound to my ears better.
Seems to make a case for manual biasing if in reality one would want the transformer to run hot. I realy don't know if this is a bad thing to run cooler.
Should I put the old EH tubes in back because the cooler condition is bad long term?
sdz
Heat is an enemy not a friend in most cases! I wouldn't be at all concerned. I'll bet the output tubes run cooler too. It's very possible that one (or more of the old tubes) was drawing excessive current.
sdz
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