In article , Trevor
Wilson wrote:

"Bill Evans" wrote in message
...

[snip]

I had thought that the practice of requiring power output in RMS to
be specified at a specified distortion level had put an end to that
type of power inflation technique and provided serious buyers with an
appropriate yardstick for comparison.

**Just a point of pedantry: "RMS power output" is and always was a
nonsensical term. The correct term is: "Continuous Watts", or just plain
ole Watts.

I tend to prefer a term like "mean sustained sinewave" power. Alas, I think
we are now probably stuck with 'RMS' as a result of all the marketing-speak
that has infected power specs in adverts over the years... :-/

[snip]


When I returned the unit (at the speed of sound) to the big box store
audio expert, he emphatically stated that I needed a "high-current"
amplifier, pointing to a much more expensive / expansive name-brand
unit that was in the same, size, weight and price range as my Akai
and Pioneer units.

As Trevor explained, the problem here is that the loduspeaker may be
nothining like a plain 8 Ohm resistor as a load. The thing to keep an eye
out for in reviews is any measurement of the 'peak current' the amp can
deliver. Hence the comment by the 'expert' in the shop.



I note seemingly incredible claims being made for home theatre
systems -seven channels at 100 Watts RMS output - "simultaneously", as
promised by a "sales engineer" in a professional audio shop that I
recently visited. I can't believe that amplifiers of this size, weight
and price on offer at this shop could possibly deliver that type of
relatively undistorted RMS power simultaneously from five channels,
let alone seven.

**Most cannot actually deliver full power from all channels
simultaneously. Most can manage full power from two channels
simultaneously.

Note, though, that some decent multichannel amps can exploit the use of
modern switch-mode power supplies, and may even use 'digital' amplifier
methods. These can allow the amp to be much smaller and lighter (and
dissipate less waste heat) than ye olde fashioned types of psu and amp. As
ever, though, the devil will be in the details when it comes to deciding if
any particular example is good for use. :-)

Slainte,

Jim

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