Does actively cooling a Class A amp negatively or positively affect the sound?

joeinid

joeinid

Super Moderator
Joined
Apr 4, 2013
Messages
18,722
Location
NY
I’ve been wondering about this for a while.

I have a couple of smaller solid state Class A running amps that I’m using for my Duo XD speakers.

Depending on the amp and where the output devices are located, I’ll run a little fan on top drawing hot air out or underneath cooling the bottom.

Do Class A amps need to run hot to sound their best? Does cooling the amp off a little affect the sound for better or worse? Does cooling the amp a little help make it sound better?

I’m curious what everyone thinks about this and if you know if any testing has been done.
 
The Valvet E2 runs very hot on the bottom. Hotter than the XA25. I can barely touch it if I don’t cool it. But it sounds fabulous. 12wpc Class A at 8 ohms.
 
Joe, have you tried raising the chassis on any kind of isolation feet just to get an extra half inch or so under the chassis? Or do you think it makes a difference at all to raise it for more airflow?
 
I have not tested it, but it is my understanding that class A amps do not need the heat for the sound, it rather is a by-product of 80% of operating energy dissipating as heat through the heatsinks in class A operation.

That said, it might not be that simple: E.g. Pass amps I used to own did not operate at their full sound potential before being properly warmed up.


Sent from my iPad using Tapatalk
 
MikeCh said:
Joe, have you tried raising the chassis on any kind of isolation feet just to get an extra half inch or so under the chassis? Or do you think it makes a difference at all to raise it for more airflow?
Click to expand...

It’s a little cooler raised up but not much.

What I’m curious about is if everyone thinks the sound of Class A amps change with the overall temperature of the unit?
 
Kuoppis said:
I have not tested it, but it is my understanding that class A amps do not need the heat for the sound, it rather is a by-product of 80% of operating energy dissipating as heat through the heatsinks in class A operation.

That said, it might not be that simple: E.g. Pass amps I used to own did not operate at their full sound potential before being properly warmed up.


Sent from my iPad using Tapatalk
Click to expand...

I agree. Getting class A amps too cool, in my opinion, don’t sound as good.
 
Heat can be the ultimate destroyer of componentry. I don't think there's anything wrong using a small, low CFM & quiet fan to supplement cooling. You won't cool the amp enough to make a sonic difference but by running a small fan blowing or sucking heat away from an amp (increasing convection) you should increase the life of the gear by removing excess heat.
 
Thank you Mike. That’s my thinking as well. Amps like the SIT3 are limited, so I’d like to make it last.
 
High school physics and basic electronics already have the answer I would think= Heat is enemy number one of electronics. Cooling a class A amp should NOT degrade the sound much less do anything to the sound (unless you don't want the amp to last very long). Excessive heat will degrade the sound faster or a noisy fan, which is an easier less costly fix. It's all nice until a capacitor starts sweating, then POP, game over.
Another question is how long it takes to reach egg-frying temperature? If it is a very short time, say 15 minutes or less, then I suspect an additional issue such as poor design or build.
Just my opinion.
 
All the amps take a while to heat up. And typically the longer they have been on, the better they sound. That’s been my experience as well as others I know.

Even Pass Labs states to give the amps plenty of ventilation.
 
joeinid said:
All the amps take a while to heat up. And typically the longer they have been on, the better they sound. That’s been my experience as well as others I know.

Even Pass Labs states to give the amps plenty of ventilation.
Click to expand...

Yes, all amps require plenty of ventilation. I had a Denon 4520ci AVR that was class B and you could cook on it after an hour if you did not cool it. at about the 1 hour and 15 minute mark it would shut down to try to protect itself. Of course, I always had it cool because I also believe that once an amp gets to that point there is a good change some damage may have already been done.

I personally don't buy into the warm up leads to better sound theory for solid state devices. In my experience, there is no difference in solid state amps between "cold" and "warmed up". To me, that is a good thing, there should not be a difference. Tubes and mechanical devices are a different story though. Just my take.
 
Components do have an optimal temperature range, and can behave differently as the the temperature changes. Overheating is a problem that is easily avoided with sufficient ventilation at normal room temperatures or a fan, especially if the fan has a temperature sensor like the AC Infinity products. Overcooling is extremely unlikely to be an issue.
 
Good topic, Joe. I’ve wondered the same thing myself. I’ll be interested to see what people say about it.
 
What does the hottest area of the chassis read from something like a digital candy thermometer? I ran an Audio Research 100.2 for a couple of years and eventually I just could not take the heat. 150w at idle. Without ventilation the heat sinks down each side of the amplifier would reach 135°F. With active muffin fan (16 CFM that was darn near silent) ventilation it would drop that number to about 115°F.

It seems strange to me for a designer to place the output transistors or heat sinks on the bottom of an amplifier since heat rises.
 
Jack said:
Or use something like these.

https://www.acinfinity.com/receiver-amp-cooling-fans/
Click to expand...

Wow, surprisingly inexpensive!

I know that my Audio Mirrors sound a lot better after 30-45 minutes. I do believe most of that is stabilizing the tubes. After that warm up time I do not notice a difference. I can not imagine a little cooling being an issue after they have warmed and the tubes stabilized. The heat sinks get toastier than the tubes :).
 
Oly said:
Good topic, Joe. I’ve wondered the same thing myself. I’ll be interested to see what people say about it.
Click to expand...


Thank you Gary. It’s one thing I’ve never really seen discussed.



MikeCh said:
What does the hottest area of the chassis read from something like a digital candy thermometer? I ran an Audio Research 100.2 for a couple of years and eventually I just could not take the heat. 150w at idle. Without ventilation the heat sinks down each side of the amplifier would reach 135°F. With active muffin fan (16 CFM that was darn near silent) ventilation it would drop that number to about 115°F.

It seems strange to me for a designer to place the output transistors or heat sinks on the bottom of an amplifier since heat rises.
Click to expand...

Next time the Valvet is in the system, I’ll take a reading. Typically my other amps reach 120-130 F. I have not measured the SIT3 but right where the output devices are in the middle of each heat sink, it damn hot.
 
You must log in or register to reply here.
Back
Top