Does an amplifier's power rating refer to it's total power consumption, or useful power output? I would think it's the latter, but I'm not sure.

EDIT: If it refers to useful power output, how much power does an amplifier actually need, compared to the rating? Tube amps, in particular, give out a lot of heat. I heard they're only about 30% efficient, if even that. Can anyone confirm or deny this?
Last edited by sashki at Jan 1, 2010,
Yeah, but they do get pretty toasty in the process, and there's a LOT of energy in heat given off, a lot more than sound or light. 30 watts of pure sound is very very loud, I think the 30 watts is the power output at the speaker, which is why speaker efficiency is so important in terms of volume.
Last edited by ProgFolk12 at Jan 1, 2010,
The power needed and power output are gonna be very different. My little 15w amp uses 40w to produce that power. If it had a higher efficiency speaker, not gonna find a high efficiency 8", then it would be alot easier to get those 15w and it would use less power.

Now a tube amp is really bad when it comes to power efficiency. If I remember right my little epi vjr uses something like 180w to produce 5w of output and it does have a high efficiency speaker, 99db.