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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!
128x128bcgator

Showing 2 responses by atmasphere

atmasphere's avatar
atmasphere
11,633 posts
 
Swampwalker, actually I agree with you on those 6C33s. They run the hottest filaments of any common power tube these days!
atmasphere's avatar
atmasphere
11,633 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...
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