What the current Aiyima A07 actually needs.

[Gruesome]

The heat does get out. The reason I added the larger aluminum block that directly contacts the case is so that the inside doesn't have to get hot and heat up all of the other components like the electrolytic caps.

I did the same thing on my DIY outdoor AVR that has 5.1 processing and 5 channels of tpa3116 all in a sealed enclosure...

-Rich

If that was true, it wouldn't have the heat problems as would no other amp (like Topping PA5).

Air is very inefficient in transferring heat as a conductor. Fans are mandatory to blow heat away (forced convection) from strong heat sources.

It's a basic principle in electronics to allow air flow to avoid overheating.

With still air, you get about 5 W per square meter surface area per degree Kelvin (or Celsius) temperature difference between the heat source and the air. (As soon as you get just a little bit of forced air movement, this heat transfer coefficient goes up by a factor 2 or more. 10-20 W/(m^2*K) is easy to get with a few m/s air speed.) Obviously, taking the air inside the box out of the equation by thermally shorting the heat source to the metal case with an aluminum bar or profile is much better, but it's not like you get no heat transport through air. You just have to do the numbers right.

 

[Jukka]

With still air, you get about 5 W per square meter surface area per degree Kelvin (or Celsius) temperature difference between the heat source and the air. (As soon as you get just a little bit of forced air movement, this heat transfer coefficient goes up by a factor 2 or more. 10-20 W/(m^2*K) is easy to get with a few m/s air speed.) Obviously, taking the air inside the box out of the equation by thermally shorting the heat source to the metal case with an aluminum bar or profile is much better, but it's not like you get no heat transport through air. You just have to do the numbers right.

Speaking of math, the A07 measures 100 mm x 40 mm x 153 mm in outer dimensions. For a smooth box this totals 0.051 square meters of outer surfaces, all of which are not fully available for cooling purposes. So if your numbers are correct and you factor the surface area into your formula, you get 10.2 W cooling power for 40 degrees of difference for the surface of the case. That's kind of bad. And that's assuming that the heat gets from the chip to the case, which is even more inefficient. Air is considered more of an heat insulator than conductor. That's why you can keep your hand just above a heated cooking stove and not get burned.

 

[Gruesome]

And with the chip being cooled via convection to the inside of the case, you have to probably double that temperature difference. And add the temperature difference from the chip die to its case. And compare that to to the maximally allowed junction temperature, probably around 150°C.
So the amp is not designed to continuously run at 100 W (assuming 90% efficiency; I haven't checked what power is claimed for this amp; ditto for the amplifier chip efficiency. These are just some round numbers).
But it could comfortably deliver a few W, with 100 W peaks, which is plenty for smaller rooms. (I typically listen at around 75 dB SPL and a tenth of a Watt, in a 110 sq.ft room. But other people might use a few W average power.)

Regarding the heat transfer coefficient, just google 'heat transfer coefficient to air', or similar, and some curves should pop up.

Anyway, the whole point was that air does transfer heat. If you are trying to use an amp like this to blast 100 W sine waves, you'll be disappointed. But for listening to music with normal power distribution (i.e. average to peak ratio), and peak power demand matched to the max power the amp can put out, it should work just fine, including thermally.

 

[john11]

I remember putting a heatsink cooler onto a cpu, in a pc build i did a few years ago. I forgot to put the thermal paste onto the cooler. The cpu got red hot.
Put the thermal paste on - all cool and quiet. Heatsinks do not pull away the heat from a cpu as well as you might think