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What’s Watts?: Myths About Power and Performance in Amplification

When choosing amplification people often place far too much importance on the advertised wattage. In this post I aim to straighten out some of the popular myths regarding wattage and amplification.

“I’ve heard this is a good amplifier, but I think I’ll get this one instead because it says it’s a higher wattage”.

“Power’s not too important because we’ve got neighbours and won’t be blasting it out”.


If you’ve already read our guide to putting together a HiFi system, you may realise that it is not so much the power of an amplifier that is important, but the way in which the amplifier is powered that will effect the sound quality. A well designed amplifier with a good transformer will be able to not only turn up loud enough, it will also be able provide power more responsively. It will respond efficiently to the changes in the music to create a sound which is dynamic, vibrant and more detailed.

You might not want to ‘blast the sound out’, but you’ll still need some power to create a good sound at low volume. A half-decent HiFi amp with a good transformer and a power rating of say 60 watts per channel (wpc) is still going to sound significantly better and give you a more enjoyable listening experience at low to mid volume than a cheap amp or mini system will.

In fact, a half-decent mid-range 60wpc amp with a toroidal transformer, will even sound better than an amp which claims to have an output of say, 160w, but uses a cheap EI transformer.

The higher wattage amp would be capable of going louder but not by as much as you might think. It might even sound terrible. The relationship between wattage and volume is not linear. If you had a 10 watt amp, you would need a 100w amp to double it’s volume, then a 1000w amp to be twice the volume of the 100w amp.

When shopping for amplification, most people place far too much importance on the wattage. Not only are there other factors which make up the performance of the amp than pure power, but the advertised wattages can often be deceptive. There are different ways to express the wattage of an amplifier.

For a start, the advertised wattage could either state the watts per channel, which is the the power for each speaker, or it could refer to the total wattage. So if you see a stereo amplifier advertised at ‘total power 100w’, it’s really a 50 watts per channel amp.

There are also different ways to measure the wattage. The main standards are peak wattage, continuous wattage and RMS (root mean square).

The peak wattage is the maximum power output that the amplifier has been measured to output in perfect conditions, in the lab, when the amplifier is running at 100% efficiency, often immediately before the amplifiers point of total destruction!

An audio amplifier is capable of producing a very large wattage for a fraction of a second. Forcing the amplifier to do this will cause component failure and is likely to produce an awful sound.

Manufacturers will sometimes advertise the peak wattage, or even total peak wattage, because it’ll look like an impressive number. In reality, the peak wattage figure is completely irrelevant and should be ignored.

To understand and compare the power outputs of amplifiers you need to look for the continuos power or the wattage per channel RMS (route mean squared). This is the power that an amplifier is capable of consistently producing, without failure.

The wattage RMS is the most accurate measurement but is still not an exact science. The relative loudness will depend on the impedance Ω of the speakers. So 60watts RMS @ 8Ω is not the same as 60watts RMS @ 4Ω. It also doesn’t tell us anything about the performance of the transformer. As we now know, the responsiveness of the power plays a vital role in the sound.

So, to summarise:

  • Power is not just about volume. Your amplifier relies on power to provide a dynamic sound with plenty of detail, even at low-medium volume.
  • If your shopping for an amplifier, ignore ‘peak-wattage’. Only look at the wattage RMS and be wary of if this is; per-channel, or the total wattage. If the seller can’t provide you with this information, walk away.
  • Don’t obsess too much on the wattage. There are powerful amplifiers that can go loud but have under-whelming performance. There are moderately powered amplifiers that are plenty loud enough for most of us and sound amazing.
  • A 120W RMS amplifier is only a tenth louder than a 60W RMS amplifier.
  • If a bloke down the pub tells you he has a 1000w amp, he likely doesn’t know what he’s talking about.

Most of all, be aware that even if you know to look only at the watts RMS, it is only one part of the story. To get the best idea of how an amplifier sounds, check out some reviews, get an idea of how much you’d like to spend, then go and talk to your local specialist HiFi retailer. They should be able arrange for you to listen to a couple of different systems to see what suits you best.

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