Pass Labs Amps - Does the heat bother you?

So.,..I’m curious why would anyone leave an amp running constantly (unless it was recommended explicitly in the IFU)?

@macg19 

It was once common practice for manufacturers of high-end solid state gear to recommend leaving their products on at all times. My Krell preamp’s manual says so, and it’s been on for about a year now, as have my Classe monoblocks. . The Krell doesn’t even have a power switch, as a matter of fact. I do turn my sources off.y

As to why, as explained before, on the whole our gear is better off being on all the time than being turned on and off willy-nilly; and there is no "waiting period" whenever an impromptu listening session strikes one’s fancy.

No one said you have to leave it on. At the end of the day, it’s your choice.

I have had a couple of Pass and they do get hot but I've never found that hot components turn into heaters.  My apartment on its own get very hot and the air conditioner is too loud to enjoy music or even the TV. So I've started to use the small fans that you put water in which are quiet enough to listen to music at an enjoyable level. I don't keep components on all the time simply because of concern of burning out the tubes on my pre and the electricity bill. I didn't know it shortens the life of SS components but that makes sense

I do find that my system sounds better after it's been on for a couple of hours. Initially it can sound flat and harsh. Am I imagining this? I have no idea. But of course it doesn't matter. It's what I hear that does.

It's not a Pass but I have a Krell KSA 300S that puts out a lot of heat when I'm playing music loud. At idle it's warm but after an album or two at 95 dB it's too hot to touch. At idle the amp uses around 400 watts. I only turn it on when I'm going to listen to music.

I am lucky to live in the land of cheap electricity (central Washington state) so this has not been too much of a problem. We get fairly cold winters so the heat in winter is welcome but it also gets hot during the summer (100+). During the summer I'm careful not to run the amp for any longer than necessary. It definitely makes the room warmer and the heat pump has to work harder. I've listened for any sound difference between startup and 1 hour later and it sounds the same to me.

I'm thinking about upgrading at some point to a pair of Pass monos. If I do this I would go with the Class A/B line partly due to the heat and partly do to the lower cost. There are a lot of very expensive amps out there that are Class A/B and I believe that we are at a point where the sonic advantage between Class A/B and Class A amps are minimal. I'm running low sensitivity/low impedance speakers so I'm going to have to go with a big amp that can put out at least 200 watts and handle low impedances. A Class A amp with this capability is very heavy, hot, and expensive.

@devinplombier I have a Krell KRC2 that also has no on/off button. I'm the original owner of this preamp and it has remained on all of its life. I had it recapped a few years ago and it's going strong. It's Class A and it's fairly warm when idle. When the shop recapped it they raved about it and said it was one of the best designed and built preamps they had seen.

@8th-note 

My Krell was moribund when I got it, it had signs of heat-related distress, the power supply PCB was fried to the point it was a miracle it worked at all, and it sounded terrible.

Reason I’m bringing this up is that, as you pointed out, it’s a Class A pre so it runs on a very substantial bias current (higher than most Class AB amplifiers, actually) and the bias adjustment trimming potentiometers (aka trimpots) had slowly drifted out of spec, boosting bias current, raising operating temperature, which accelerated the trimpots’ failure, further increasing bias, etc. causing extensive damage over the years. I had my work cut out.

Your shop should have replaced the trimpots when they did the recap. If they did, you’re good for another 30 years! But if your pre still rocks original factory trimpots. I would recommend checking its temperature with an IR thermometer every month or two. Since you keep it on all the time the temperature should be very stable. If it starts getting sustainably hotter for no apparent reason, it’s time to have it looked at.

I totally agree that it is one of the best designed and built preamps - in addition to sounding glorious :)

My XA 30.8 doesn’t produce the heat my 300B mono blocks do and in either case the heat produced in minimal. The joy of hearing what the 30.8 brings to my listening sessions far outweighs any concerns or perceptions about it producing heat. If you are inclined to try Pass Labs I encourage you to!

Disclaimer: as you read the following, know that we’re Pass Labs dealers.

I have similar experiences with our Pass XA-25.  It puts out  quite a bit less heat than our NiWatt 300B amps do.

Having said that, more output devices (more power) = more heat.  The question becomes how much is too much, and what your alternatives are.

If you were to go with a large tube amplifier with a bank of KT-88s, then you’ll also be putting out a lot of heat.

If you go for a class A/B design, there are sonic compromises.  Of course, if your amp runs mostly in class-A (like Pass’ "X" series) before switching over, then you can sidestep these issues for the most part.

I have no experience with class-D amplifiers.

When you get to the point of considering a ~300 watt amplfier, it’s time to ask yourself some questions.  Is it time to consider a speaker swap?

We do our best here at Galibier to expose audiophiles to the joys of high efficiency speakers - smaller amplfiers, with less dyanmic compression, and the thing no one seems to mention about high efficiency speakers:  late night listening at lower volume levels becomes more satisfying.  It's not just about loudness per watt.

Thom @ Galibier