Measuring Power

[FunkyE9th]

How do you guys measure the power of the amp? Is there some industry standard out there? Do I just pump 1KHz (or some other tone) into an amp with a dummy load and calculate the load power right before it distorts?

Thanks,

-FunkyE9th

[Andy Le Blanc]

its a good question....
I'm sure that most look at tube data and use their best swag
volts across a load looks ok but Im sure there are better ways too

[Bob-I]

The way I was taught is to put the amp on a scope, on a dummy load and inject a sine wave. Adjust to just before distortion then measure the peak to peak using the scope. Divide by 2, then multiply by .707 and calculate the wattage using ohms law. Here's a handy calculator http://ourworld.compuserve.com/homepage ... hmslaw.htm

That's your RMS power.

I've done this a few times and ended up with very close to the theoretical power. For example my 2x6550 bass amp was expected to be about 85 watts, I measured 78watts.

[FunkyE9th]

Bob,

What's the frequency of the sine wave that you use?

Thanks,

-FunkyE9th

[Andy Le Blanc]

here an older definition of audio power.....
in terms of energy imparted to air by the speaker
so how do properly set up a test scenario with say a decibel meter
what would be a standard test format that all can use
you could have little amps out perform larger ones based on the speaker efficency

[FunkyE9th]

I would think you'll need a special room for that type of measurement. Perhaps an anechoic chamber with decibel meter at a specified distance (1Meter?). But this would be SPL (in Pascals) though rather than watts though, right?

[Andy Le Blanc]

decibel meters are to bad of an exspence..... but a standard method
You dont have to test to an ideal condition
that along with the electrical information of the unit being tested
would be good
could compare results from measured numbers and performance
I ve seen some where a way to go between decibels and watts

[Bob-I]

Bob,

What's the frequency of the sine wave that you use?

Thanks,

-FunkyE9th

800-1000Hz.

I've swept through the entire usable range of the amps and seen very little difference.