question for SLP05 owners:

If it were me and you see any type of ventilation holes under each of your units, maybe consider ways of ensuring sufficient air gets in.

Yes, we’ve both seen photos SLP-05/Power supply stacked, and I just checked a few reviewers that had them on display not stacked closer together. Maybe you can gap them some if you must stack. Same as some rack mount computer blade systems in racks within big Colo data center facilities. Moving Air is your friend if you want equipment to last.

If you do decide to stack, maybe you could do something like this for each, some kind of risers underneath each one, then stack, sort of like this. Can’t find a good photo but you get the idea. Stuff inside these units melts ages, cracks, over time from heat, this we know.

I appreciate your input, @decooney . I am starting to think that I don’t like the idea of something that gets warm sitting right on top of something that gets hot. When I say hot, I do not mean hot enough to burn flesh, but hot enough to make the palm of my hand feel a bit uncomfortable, and for someone who is not particularly sensitive that way, I guess that’s getting pretty warm. I need to remember to put a thermometer on top of it once to see what it actually reads. It must be those two big caps, huh? I cannot imagine that the 5AR4 is what makes it get that hot.

Anyway, I can find a way to reconfigure without stacking, but thanks again for taking the time to offer input and post the pics.

No worries @immatthewj I was typing this as I rotated my tube monoblock amps out, inserting and warming up my other Class A 50w solid state amp on/off past few days.  That SS class A gets to about 45-47C on the heat sinks as biased, and ensuring I have nothing above it or near it. Above it sits my Cary SLP-98L preamp, I keep the power supply away and sufficient air above it to breath in a similar manner. I use to stack some other dual mono HT SS amps I had years ago, not any more. Burned out one of them on the top of the stack, learned a lesson.   

As for heat, you might compare with others with SLP-05s and see if anyone has used a Infrared Thermometer Laser Temperature Gun and checked temps at all across different surfaces, tubes, etc.  

Are you running a different set of tubes, rectifiers, in it now then compared to the past and do you suspect more heat after trying different tubes - or anything like that?   

They were made to be stacked . I recently sold mine to a buddy who has them stacked just like I did for years.

The reason Cary Audio changed the plate on top of the power supply to one without “foot indentions”, was to discourage people from stacking for the sole reason that sometimes the transformer radiated noise into the preamp above.  When people would complain about hum being radiated into the preamp from the power supply, and we’re told to move the power supply away, they would question “then why are there indentions on the top plate for it to be stacked?”.  So Cary Audio changed the power supply top plate to one without indentions so people wouldn’t stack them or question anymore.  Thus, no more hum issues. 
Heat typically wasn’t the problem although they do get hot because of the rectifier tube in the power supply.  The power supply umbilical cable was made by Kimber Kable for Cary Audio and is pretty good non-shielded wire. 
Some people change the rectifier tube to a solid state type (for sound change purposes) which also runs cool and can make the preamp sound more detailed with much tighter bass.  It’s something to play with you like.  I use SS rectification in mine using high speed rectifiers. Not HexFRED’s but similar. I had an old “Weber Copper Cap” that I upgraded the rectifiers in that just plugs into the octal socket in the power supply.  You can use one of those made by TubeDepot or whatever.  In my system I love the speed, imaging and detail it presents but every system is different. If you already have an overly bright sounding system you probably won’t like SS rectification on your SLP-05.