Question about power ratings?

The honest answer is no. Most manufacturers can rate their receivers/amplifiers differently in order to get a larger number. I wouldn't worry so much about the power ratings and just listen with your ears and pick the one that sounds best to you. Good luck!

There is a big differenece in the two power ratings which should be of concern. The first rating is saying it will deliver 120watts X5 only at 1kz (one frequency) which 1khz is the easiest frequency to drive. The other amplifier is saying it can deliever the same out put across the whole frequency range that we can hear from 20 to 20khz.

Be very leary of amplifiers that give such a rating at one freqency as this usually indicates a very poor amplifier.

The second listing is better.

Power - varies by the frequency. Low frequency takes a LOT more power to produce the same volume. This is why we have self-powered subwoofers but not self-powered tweeters.

A more challenging way to measure output power is to promise X watts while producing a broad range of frequencies.

With respect - power ratings ARE useful, but you have to know that there are 5 different variables involved and make sure both ratings use the same conditions: Number of speakers, range of frequencies, Total Harmonic Distortion, Impedance of speakers, and PEAK vs RMS power.

Another rule of thumb: If two amps publish the same specs... look at the weight and buy the heavier unit.

One of the big devices in a amp is the transformer which is a massive piece of metal. The heavier one will run cooler and handle dynamics better.

Hope this helps.

First listing better. Receivers are not even fan cooled and have heatsinks the size of 50 watt amplifiers. Anyone who can do homework knows to have that much power you need some bigger heatsinks, with fans even. even Looking for RMS won't help, that term is useless and is a shortcut to try and find DC power and just slap it on an amplifier (AC Feedback)

and thirdly,

Power doens't vary by frequency! wavelengths increase and decrease what is known as frequency, amplitude, however requires more power, which is volume. which explains itself because the human ear cannot hear bass freqs below 80 hz or so at low volumes or even mid for that matter. Amplifiers are made to compensate (MOST) for this loss, so bass is the first to distort always.

Listen to them and choose. Worse looking specs can sound better because the company is publishing true specs, but afraid of losing business in a high pace market.

Rating on speakers and receiver are at times useless. Human ears can't hear below 20HZ and above 15K HZ. The .05% total harmonic distortion as rated, you won't be able to hear anyway. Look for total RMS rating on receivers or speakers for the low budget type. Let your own ears be the judge. Hope this will help.