Pass Labs Amps - Does the heat bother you?

The answer to this question is this: 

it depends;

Does the evening sun hit the windows of the listening room?

Size of the room

Model of Pass amp: an x350.8 runs about 55C in an ambient room of 25. So around 30C above ambient. If the room goes up 5 deg C so does the amp. So on and so forth. A Pass X350.8 weighs over 105 pounds, has a large surface area and large heatsinks. The amp will liberate at least 400 watts at idle. So around 1,400 BTU. This is a significant amount of heat in an average size room with doors and such. 
If your listening space is wide open, basement, no sun on walls and windows,

you live in a generally moderate env like northeast the 350 will probably not make any noticeable difference.

If you listen on a higher floor level in house and have a smaller room and sun warms this part of your house the 350 will likely increase the temp. 
so why don’t you tell us your listening space specs and your will get a more accurate response. You can also enter your room dimensions into ChatGPT with whatever amp and its idle dissipation and size and your nominal ambient temp and it will accurately compute the time to thermal equilibrium and temperature. Give it a shot. Tell us the results.

Not in the winter 😳

This is nuts. Class A amps get hot. How hot? I have a Pass INT-60, admittedly an integrated, but I could leave my hand on the thing all day long and not flinch. When you go up in output you’re gonna get more of that. The sonics are beautiful. I’m in Texas. If you’re into this and that’s an issue, get a damned fan, or get a life. The main issue here is size and weight. That should be the main conundrum, not the heat. Adequate ventilation solves that. Worrying about heating your room puts you into another category of idiots.

Like others have mentioned, the size and location of your listening room will make a huge difference.

I own the Aleph 2s, again. The first time was in Germany where my listening room was in the basement. The size was appx 15x17. I left them on 24/7 and never had any heat issues. Sold them because I liked the VTL's I had just slightly more. Regretted that move.

Fast forward 20 years and now the listening room is a small 13x14 room. I came to own the Aleph 2's again. In this small room it raised the temp by quite a bit, making it uncomfortable in the summer. 

The only way to solve the issue is to run the window AC while the amp is on and turn off the AC while listening. I also turn the amps on/off when not in use. 

I owned a Pass X350... it did not get beyond slightly warm even when driving at high volume. I left it on for ten years, before upgrading.