I was checking out an amplifier rated 160+160W peak power, or 320W bridged. I wanted to know what the RMS output of the amplifier is but it's an old amp and there's no info about it on the web. I figured there had to be some way to calculate RMS from peak power, so I kept surfing the web. Then I ran into this:

http://www.radioelectronicschool.com.../reading10.pdf

Now if I'm reading this article properly, it appears that the RMS output of an amplifier is the amplifier's peak power output times 0.707, or to put it in the form of an equation:

RMS = 0.707 X Peak

If that's the case, an amplifer with 320W of peak power should be putting out 226W RMS.

Whatcha think? Does this formula apply to power amplifiers? If not, why not?

 

I wouldn't trust that. If you look at the specs for a lot of amps, you'll see their peak power is like double the RMS power. That would mean that the formula is peak power times .5, not .7. Here is a good amp to use as an example. Max power says 1000W, but RMS is 460. That would say it's peak times .46 . Therefore, I would not trust that formula. I think amp companies just like to put the absolute, once in a life time, on it's best day power rating. If I had to guess, I would say that amp is closer to 80x2.

http://cgi.ebay.com/ws/eBayISAPI.dll...category=18796

 

When I took circuits in college RMS power equalled peak power divided by the square root of 2 (which is equivalent to multiplying by 0.707). Maybe the companies can legally claim a higher peak power to trick unsuspecting buyers?

 

I will agree that in theory, RMS is .707 of peak. For some reason, however amp rating prove against that. Why? Good question!

 

What I was told one time is some manufactors use Vp-p (voltange, peak to peak) so that the number comes out higher (think of a wave) now I think you'd have to do a bunch of math to figure out what the real rms (using whatever resistance it's rated for) rating is but I think a good rule of thumb is a little less than half.
(Sorry told this a long time ago, and it's late)

 

you guys are alll correct. in a perfect circuit rms is peak x .707

but this isnt an ideal world, and manufacturers use different ways to calculate rms value, it is usually less than half of peak

 

Read this: Real World Power
Though I did find his voltage estimates to be off. My amp displays the voltage it's seeing, and it's almost always over 14 volts. So do your math with that.

 

Cool. Thanks.