What Is The Actual Power Of Your Amp?

Too many receivers, amplifiers, soundbars list bloated power rating. One home theatre in a box, for example, print its power to be 1,000 Watts…which is impossible for something that tiny in a plastic box and NOT being a digital amplifier. Furthermore, the power consumption is rated at a mere 150 Watts maximum.

It is absolutely impossible to get 1,000 watts out of 150 watts of power consumption. If anybody can produce that much power from such tiny source, that person/company can solve the world’s power crisis.

To make long story short, as previously mentioned, the only documentation I can find is its maximum power consumption. So what a consumer should do?

Well, if the amplification system is a class A/B type like most systems are, you’ll need to divide the maximum input power by two as class A/B at best have 50% efficiency. Then if it is rated at 10%THD, divide that number by two again as lowering the unacceptable 10% THD to 0.1% THD will half the output power once again. Then divide that final number by the number of channels the amp has. In this case, 5 channels.

So:
((150 W x 0.5) x 0.5 ) : 5 = 7.5 Wpc max at 0.1 THD.

Therefore the advertised 1,000 watts is actually only 7.5 watts per channel…if you’re lucky because the formula is based on best-case scenario.

Another example, a 5-channel power amplifier claim to have 170 watts per channel rated at 1 channel driven with no other specification stated anywhere.

So, what you need to do is go to the manual and look at the maximum power consumption (by law any amp manufacturer have to have it listed in the manual). In this case, the maximum power consumption is listed as 850 watts at 10% THD.

So using the same formula:

((850 x 0.5) x 0.5) : 5 which gives us the end result of (in the best case scenario) a scant 42 watts per channel running at full spectrum at 0.1 THD.

Of course the numbers are just an approximation, but at least it will give you the more accurate real-world power output.

Don’t believe in the hype, calculate it yourself!

Note: the formula above is applicable to class A/B amp only. For Class D amp, use the formula below:

((Max power consumption X 0.8) X 0.5) : number of channels = true approximate power output. 