Caps don't put out heat. At least not enough for a human to notice. All caps have a small parasitic resistance and, thus, technically create some heat. But, probably less heat than my fingers generated while typing this message. I think electrolytic caps dry out because of heat radiated from other nearby sources or just evaporation over time.

The temperature rise in an amp has more to do with effiency rather than power output. Take for example the Crown K series amp.

Power rating
Stereo Mode (Per channel at 1 kHz with both channels driven to 0.1% or less true THD)
K1: 750 watts into 2 ohms, 550 watts into 4 ohms, 350 watts into 8 ohms.
K2: 1,250 watts into 2 ohms, 800 watts into 4 ohms, 475 watts into 8 ohms.
Bridge-Mono Mode
K1: 1,500 watts into 4 ohms, 1,100 watts into 8 ohms.
K2: 2,500 watts into 4 ohms, 1,600 watts into 8 ohms.

The K2 will put out up to 2500 watts yet if does not use a fan to cool it because it uses an efficient class D power output stage.

For a given amount of heat (inefficiency) in a box there are may ways of getting the heat out of a box. A fan is often the simplest way to do this but with proper thermal design techniques there are may other ways to create air flow within a box.

Some facts and explanations:

Class D is efficient, but not as accurate as class A or AB - see this link for info

[Link: hometheaterhifi.com]

About the Denon 5800 - it has 2 fans, and I could never hear them at any volume.

The web site that you reference makes the statement about class D amps

"However, distortion at the crossover point (+ to -) can be introduced because of "dead time" which is caused by the fact that the + and - transistors cannot ever be on at the same time."

This shows a total lack of understanding of how a class D amp actually works.

Westie, the K2 amps last time I checked which I have 2 of them did not have fans.

Bryan: don't remember exactly, but I believe it is under 70 lbs. The box says "two people required to lift"... .

Another analogy given me about the heat generated in a receiver concerns todays PCs. The chips and hardware generate a lot of heat, and as you know, there are a lot of after-market cooling devices (as well as the built-in fans) sold that help dissipate the heat build-up. When I look inside a modern-day receiver or amp, I see a lot more heat-generating hardware than my PC! ... Mike

I'd forgot about this thread.

Brian: When I had the 3801 in at the same time as the 3300, I looked inside both and the size of the heat sink is the same - the DESIGN is different. If you look through the air outlet at the back you'll notice a more efficient air flow over the cooling fins - in fact two of the fins don't stick out as much so the air more easily flows over the entire heat sink.

And there is a fan housing in exactly the same place as there is on my 3300. So, unless someone has actually open up a 3801 and can tell me why they would still put the fan housing in but have not fan in it, your 3801 HAS a fan.

But, read my message above and that is probably why you think there is no fan (and other people think).

When I had the 3801, it was just warm (with no fan running), compared to my 3300 which gets hot (and the fan has to turn on from time to time).

... Greg

The transistor has been shipped to the repair depot. I will get the "fan fix" and report back here as soon as I do so. BUT... I will be waiting just a little bit, because the UPGRADE for the Onkyo (and the Integra) is due within the next couple of weeks, and I don't really feel like doing all that device pulling and re-wiring twice.... I'll get both fixes at the same time. Wowzer... ... Mike

I know this is an old post, but I had to post an update.

I am getting ready to trade in my 3801 for the 3802, and when I pulled it out, I was looking inside. Sure enough, I see a fan housing. But I can't see if there is a fan there or not. I see two wires (red and black) going to the housing, so I have to assume that there IS a fan in there. I'll be damned! I have to eat crow here and put my tail between my legs. I guess everyone is putting fans in their receivers!

I will say though, that my receiver has never gotten hot, and that I have never once heard a fan come on. Even when I open my rack after playing for a while, there is not any heat build up in there.

Just had to update to set the record straight.

Thanks,
Bryan

Aaaahhh... an honest man.

Yep - couldn't let this one go - cause I know I was wrong and have no problem admitting it!

By the way Mike - have you gotten the fan fixed yet - or are you still waiting for the software upgrade? I thought I heard the upgrade was actually out now, but I may be wrong.

Bryan