Why do audio interfaces run so hot? (i.e. which component causes the heat?)

[Scoox]

Per the title, I've had many audio interfaces over the years, some ran nice and cool while others got pretty toasty, even while idling. For example, my RME BabyFace Pro barely gets warm, but my RME UCX II gets hot even with minimal onboard DSP resources in use. My former Fireface 400 could get hot enough that it would feel uncomfortable putting my hand to it, and yet it was still working after 15 years (sold it used and fully working). Looking around it seems other interfaces by other brands get hot too. I haven't measured with an infrared thermometer but but my UCX II gets hotter than the back of my laptop feels, and a hardware monitor reports my laptop's "package temperature" to be about 65 °C.

This makes me wonder, which electronic component of the audio interface is responsible for generating this much heat? Is there anything that can be selectively disabled so it runs cooler?

 

[mansr]

my UCX II gets hotter than the back of my laptop feels, and a hardware monitor reports my laptop's "package temperature" to be about 65 °C.

Package there refers to the outer surface of the CPU chip, not the exterior of the case.

This makes me wonder, which electronic component of the audio interface is responsible for generating this much heat?

Probably the power supply.

 

[Scoox]

Probably the power supply.

It's a soap-on-a-rope power supply, barely warm. Obviously there will be some kind of switching regulator within the interface but I doubt it'd be this inefficient.