give me an amp make and model and I can look it up 500 watts peak.. at what load? if it just says "500 watts" and its a two channel amp here's the breakdown: 250w x 2 peak @ 2 ohms maybe 150w x 2 @ 4 ohms peak that'd be about 50 watts x 2 @ 4 ohms RMS

it really depends on the amp itself. need more information to be able to tell you. peak can be anywhere from two to over four times the RMS power, and that will also vary based on load.

my my glass aren't you being kind today, he never mention weither or not he is talk able an amp. i thought he was trying to pass his basic electronic finals.....

Its a amp I got from wal-mart here in Germany. It does ok so far until I can afford a better sub and amp. Its a Toxic amp TX-500. 500 watts peak when bridged, can only handle 4 ohms when bridged, its a two channel amp, each channel puts out 250w but each channel can handle a 2 ohm load.

well Demi, this is the amplifier forum, so I figured he was talking about an amplifier.

Toxic.. hmmm looks like some British brand.. not a USDM product. if it's 500 watts RMS bridged to 4 ohms, it's probably about 125 watts x 2 @ 4 ohms best bet is just to search the manual for a website or an RMS power rating for the amp. it must be listed somewhere surely.

Like Jonathan said, .707xPeak=RMS. That's for a simple sine wave. It doesn't matter the source... that doesn't change the equation. Audio is just a bunch of sine waves layered on top of eachother. So the equation stands.

Doug, that equation doesn't hold true for audio manufacturers heheh "peak" or "max" output, sometimes called "PMPO" and so forth can be up to four times the RMS power output. How they actually derive this number is a tightly held secret though, and apparently involves a crystal ball, an elbow-length rubber glove, and a very dark smelly orifice. That's strictly rumer though so don't quote me on that.

Joh was just pointing out that with a car audio amp, you can't always rely on the .707 calculation to get an acurate number. Especially not when the amp makers only say "2400 watt amp!" and don't mention how many channels, at what load, etc.. it usually breaks down to about 200 watts x 2 at best in reality.

The only reason car amplifiers don't "hold true" to the equation is because they're so massively overrated. Peak and RMS (root mean squared) still have static definitions. If you were to actually measure the output instead of relying upon ratings than you could use the equation. Try using an Oscilloscope to find out what your amp is actually putting out. You'll see that it's nowhere near the ratings.

actually peak output for an audio amplifier varies because the power supply is often unregulated, and at peak demands the power supply will alter the amount of power the amplifier is producing. the whole calculating the RMS of a sine wave deal mentioned above is for calculating a static sinewave RMS. It doesn't take into account a myriad of other attributing factors that affect the final outcome like the power supply and input stage of the amplifier. RMS power ratings can also be measured in a number of ways, which will affect the outcome, such as if the signal being used at the input stage is a narrow frequency generated tone, or pink noise, or music, etc. There are many factors to getting an accurate RMS rating of a power amplifier. It's not quite like reading the AC peak and trough on a simple op amp circuit in high school. I'm well aware of measuring RMS with a scope though. Done it plenty of times working on units in the shop. anyway, as to the original post, there's no way to know the "RMS value of the amp" based on a mfg spec calling the amp "500 watts peak." There's simply far too little information given regardless of any of the other sematics above.

There really isn't a way to bench test an amp for peak power anyway, not to relate it to RMS, anyway. The typical RMS equation for AC circuits is in circuits with a consistent power supply (such as a 120V AC source) that never fluctuates. An amplifier has to generate signals with constantly changing power levels, and the peaks can actually go higher than the equation theoretically would allow it to (but not to the extent of that 1800 watt Legacy above). That's why you should never go by peak output, it's instantaneous and really has no relation to the true average output of an amplifier. Remember than an amplifier is only so efficient. Assume an amplifier is 50% efficient on average, and is running off of 12V and draws 10A of current (for easy math). The amplifier average would be around 60 watts. But assume this efficiency is raised for a VERY brief moment (say on a extremely hard bass line) to 100% (this will NEVER happen, it's just an example) then the power would be 120 watts, double the power. 120 x .707 would be 84 watts, more than the equation would allow and not a true RMS output. The equation is even more thrown off when an amplifier is less efficient. LOL at Glass, I love the way you worded your description on deriving peak ratings.