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Tube amp heat questions...

Hi all, I recently joined the ranks of tube amp owners by adding an ARC VSi55 to my setup. Love it, and it doesn't seem to put out a ton of heat, but it's getting cooler here in Phoenix so I may feel differently next July.

I did search thoroughly through past threads to see if these questions were asked, and found some good threads about summer amps vs. winter amps, but not my specific questions:

- Is there a direct correlation between tube amp wattage per channel and heat generated, such that for example any 100wpc tube amp will always put out more heat than a 25wpc tube amp?

- If that is the case, it is because higher WPC = either more tubes and/or larger tubes?

- If that is not the case, is heat a function of tube type, such that certain 25wpc tube amps can generate more ambient heat than a 75wpc amp just because of the type of tubes it uses?

I didn't take these questions into account when purchasing the VSi55, but we may put together a 2nd system for another room and I may take this into account for that purchase. And as others have done, having a nice Class-D amp for the June-Sept period is also a possibility. Thanks in advance!
bcgator
atmasphere's avatar
atmasphere
7,068 posts
 
Bcgator, air conditioning is a brute-force method of dealing with heat. In the old days people simply had vents in the ceiling. A simple solution, inexpensive and one that works really well. Even in the 21st century, heat still rises :)

You will find that there is a loose correlation to the sound of the amplifier and the class of operation. I say loose as there are other variables that can have a big effect on the sound. Generally speaking though, amps that are class A (make the most heat) tend to sound better than amps that make the least heat (class D being an example).

It is not the filaments of the tube that make the heat in a tube amplifier. It is the class of operation and how efficient the amp is running (the two are not always the same). You can make the amp run more efficiently by using a loudspeaker that is higher impedance and higher efficiency. Almost any tube amp will run with less heat into 16 ohms for example, because the output transformer will operate more efficiently- more power makes it to the speaker and less is dissipated as heat.

Conversely, any amplifier (tube or transistor) will make more heat if asked to drive a four ohm load (assuming that loudspeaker efficiency is otherwise the same)- and it will make more distortion which results in less detail and harsher sound.

So your speaker can play a big role in this. If its easy to drive, generally speaking you will get less heat from the amp and better performance too. Something to think about...
sfar's avatar
sfar
1,352 posts
 
I can't add to the excellent technical information you've received but just as a point of interest I recall using an infrared thermometer like the one Viridian suggested to check the temperature on one of my tube amps.

In an auto-bias AES/Cary AE-25 amp running at idle in triode with a stated power of 15 watts from KT-88 tubes the temperature of the output tubes was somewhere close to 300 degrees Fahrenheit.
swampwalker's avatar
swampwalker
5,132 posts
 
Like Sfar, I can't add to the technical side of this discussion but I will tell you that, IME, in my system, there are 2 extremes in tube amp heat production. Coolest running is the Berning ZH-270. Hottest are Joule OTLs using 8, 10, 12, 16 of those big ole beautiful Russian 6CC3Bs. With some trepidation to be contradicting Atmasphere, in that case, the output transformers, being absent, have nothing to do w it. Those tubes are just little furnaces; even the Almarro 318s that use only a pair can heat a room!

I suspect that those examples are outliers with good technical reasons for being so. The difference is night and day (or winter and summer). In general, I'd stick w the advice you've gotten above. But, I will say that if I lived in the south, I'd probably never have sold my ZH-270. Out of production, so hard to find, expensive ($4-5K), and not compatible w all speakers, but probably the best tube amp I can think of for your situation. A less expensive but also hard to find option might be a high eff speaker w Berning's Microzotl, which uses a pair of 6SN7s as output tubes!! In a small room at my house at the beach, that little amp sounded pretty darn impressive driving a pair of 96 dB back-loaded horns. Now my taste runs to singer-songwriter/fold/acoustic type music at moderate SPLs, but in the right circumstances, it might be option. They show up here from time to time at just under $1K; since they were primarily marketed as a headphone amp, you might have better luck looking for one on head-fi.org. Good luck, have fun, and stay away from those nasty transistors ;-)
bombaywalla's avatar
bombaywalla
1,957 posts
 
Good luck, have fun, and stay away from those nasty transistors ;-)
Swampwalker
Hey, hey, hey - be nice, swampwalker!! :-D LOL!
those little silicon gems are nice if you know where to buy the right kind... ;-)
swampwalker's avatar
swampwalker
5,132 posts
 
Bombaywalla- No offense intended to my vacuum-challenged friends here on the 'Gon. Oooops, I did it again!
I was TRYING to be nice, but I'm not very good at it! LOL. I almost said "friends don't let friends listen to solid state".

BTW, I'm sure you're right: I did hear ONE ss rig (Class D no less) in NY last April that I liked. Oh, no, I'm incorrigible. Sorry.

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