RMS 'n Peak Ratings

[smaz]

On my amp, it says it has 180 watts RMS and 300 watts peak. What is RMS?

[Don Corleone]

Root Mean Square

[smaz]

Ahhhh I understand now....

What's that mean?

[kentuckyklira]

Re: RMS 'n Peak Ratings

Originally posted by smaz
On my amp, it says it has 180 watts RMS and 300 watts peak. What is RMS?

There´s a certain limit to how much power your amp can generate without distorting the sound. That´s more or less the RMS level. Peak means how much power your amp can generate regardless of the sound!

[smaz]

So on full blast, it's 300 watts, but at the point where it still sounds good, it's 180 yeah?

[kentuckyklira]

Originally posted by smaz
So on full blast, it's 300 watts, but at the point where it still sounds good, it's 180 yeah?

Well, if it´s a tube amp then the distortion might be what you´re looking for.

But with solid state, you´re more or less right.

[BrownSound1]

While it is true that RMS ratings a lot of times will have the percentage of THD (Total Harmonic Distortion) it doesn't mean that the amp is producing that amount of power without distortion. I've seen ratings for cheap stereos that said 140 watts RMS per channel @ 2% THD. That's not a good spec for clean output, but the company has that rating none the less.

There are a lot of misconceptions on RMS and Peak power, so here are some explanations in laymans terms. Hope it helps.


Peak power is the amount of power that an amplifier can produce for a brief burst....like the intial bang of an E chord or let's say on a stereo the initial pop of a snare drum. Certain signal types require more power to produce at the given gain setting.

RMS is the amount of continuous power the amplifier can produce. This is the number you should consider as the actual wattage your amp puts out. In theory you could inject a signal and output, let's say 180 watts all day long, and not really damage the amplifier.

The output power of an amplifier changes as the signal going into it changes. Bass frequencies usually require more power amp power than do upper frequencies. It is quite possible to hit the peak power of an amplifier at low volume settings.

[kentuckyklira]

Originally posted by BrownSound1
While it is true that RMS ratings a lot of times will have the percentage of THD (Total Harmonic Distortion) it doesn't mean that the amp is producing that amount of power without distortion. I've seen ratings for cheap stereos that said 140 watts RMS per channel @ 2% THD. That's not a good spec for clean output, but the company has that rating none the less.

There are a lot of misconceptions on RMS and Peak power, so here are some explanations in laymans terms. Hope it helps.


Peak power is the amount of power that an amplifier can produce for a brief burst....like the intial bang of an E chord or let's say on a stereo the initial pop of a snare drum. Certain signal types require more power to produce at the given gain setting.

RMS is the amount of continuous power the amplifier can produce. This is the number you should consider as the actual wattage your amp puts out. In theory you could inject a signal and output, let's say 180 watts all day long, and not really damage the amplifier.

The output power of an amplifier changes as the signal going into it changes. Bass frequencies usually require more power amp power than do upper frequencies. It is quite possible to hit the peak power of an amplifier at low volume settings.

That´s why in Europe we usually consider sinus as the appropriate figure. That´s the level at which the amp will still generate a clean sinus signal.

[BrownSound1]

You mean SINE signal...as in a SINE wave. RMS is going to be the same in Timbuktu, and they measure it the same in Europe as well. That's why I pointed out that there will be a THD rating with the amplifier.

Most of the time they will display some input voltage that the measurement was taken at. For instance an amplifier rated at 100 watts RMS at 10 volts is louder than an amplifier rated at 100 watts RMS at 14 volts...if you put the exact same level of input to it.

[Nitro Express]

In short, it's just an average measurement. Kind of like horsepower on a car. It all depends what the RPM is but people like to label things and why not just give them an average. It makes the sales people and marketing peoples job easier. KEEP IT SIMPLE STUPID. Bubba wants a 100 watt Marshall that goes to 11. He don't give a shit about peak wattage or input power. But if someone has a 200 watt amp that goes to 11, damn it to hell, he's going to get a 300 watt amp that goes to 11, even if it means it's the peak wattage and the incruments on the volume potentionmeter are made smaller. LOL!

[kentuckyklira]

Originally posted by BrownSound1
You mean SINE signal...as in a SINE wave.

Sorry bout dat dude. In German it´s "sinus" and 8track tapes were still around when I left the USA!

[Hardrock69]

RMS should be considered also when buying speakers. If you buy a speaker with a rating of 100 watts peak power, and run a 100-watt amp through it, it will melt the cheap pieces of shit if you run the amp at 10. So you would want to get speakers rated at 100 watts RMS, NOT 100 watts peak.

Many speaker manufacturers will lie to you by claiming a certain speaker si a 300-watt speaker, when that is actually the peak rating (check the specs and the fine print), and the RMS rating will be much lower.

[BrownSound1]

Originally posted by kentuckyklira
Sorry bout dat dude. In German it´s "sinus" and 8track tapes were still around when I left the USA!

No problem man, just messing with you a bit.

[Panamark]

Good explanations guys !

I was going to say think of RMS as average, and Peak as the absolute
highest output the amp can generate in a short burst.

But you fuckers explained it better than that