Appreciate your comments and those of others on this thread, but most
comments seem to focus on the definition of RMS, not the basic issue of
misrepresenting power output capabilities of modern amplifiers. What I
recall from the late seventies is that the International Institute of High
Fidelity (IIHF) had established detailed technical specifications that
defined the measurement techniques that would necessarily be used to
establish the specified amplifier power output on an RMS, continuous power
basis. This specification process was, as I recall, very rigorously
described.

What happened to IIHF? Is there no accepted industry standard, either in
Europe or North America or elsewhere on rating audio amplifier output power
levels?

"Ian Iveson" wrote in message
. uk...
Roderick said

RMS values of the current and voltage are used to calculate the mean (or
average) value of the power, because these values of voltage and current
are
equivalent to the DC values that would supply energy at the same rate, so
"mean
power level" is the quantity that should really be specified.

Yes. If you square the root of the mean square you obviously get the mean
square. Since the square is proportional to power, you get mean power.

There is real and meaningful confusion in this RMS power nonsense. Pure
inductors and capacitors dissipate no power, although they may have
voltage across them, and current through them, simultaneously. This is
possible because positive and negative power cancels. RMS power would not
cancel, because it would always be positive. Hence it is not a trivial
confusion. It is indicative of a serious lack of understanding of basic
essentials.

My first question in the hifi shop is always "what kind of power is that?"
If man says "RMS" I walk out. Hence I now have to make all my own hifi.

cheers, Ian

In article , Bill Evans wrote:
Appreciate your comments and those of others on this thread, but most
comments seem to focus on the definition of RMS, not the basic issue of
misrepresenting power output capabilities of modern amplifiers.

Quoting an amplifier's output power in "RMS Watts", or as "RMS power", or
simply appending the magic letters "RMS" to some quoted power output value
*is* misrepresenting it, because these expressions, although having tha
apparent authority of technogobbledygook, are actually meaningless.

Rod.

In article , Bill Evans
wrote:

What I recall from the late seventies is that the International
Institute of High Fidelity (IIHF) had established detailed technical
specifications that defined the measurement techniques that would
necessarily be used to establish the specified amplifier power output on
an RMS, continuous power basis. This specification process was, as I
recall, very rigorously described.

Can't comment on the 'IIHF' apart from noting the the real problem is
likely to be that such bodies may have no way of 'enforcing' their
decisions or standards on manufacturers or shops.

What happened to IIHF? Is there no accepted industry standard, either in
Europe or North America or elsewhere on rating audio amplifier output
power levels?

Pass. The IHFA (not IIHF) did set a series of regulations on how to test
powers back in the 1970's. (IHFA-707 IIRC) These were very demanding, and
some of us did use them for a while. However they were so demanding that
people seem to have decided to stop using them.

This is one of the areas where the audio magazines *could* help if they so
chose. They could adopt a suitable set of test measurement standards and
apply them. Then both publish the results, and 'name and shame' makers whos
published specs were twaddle.

Alas, the track record is that mags tend to prefer to publish 'subjective
auditions'... Pretty useless for prospective customers, and apply no
pressure on makers whatsoever... :-/

Slainte,

Jim

--
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Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
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Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

In article , Jim Lesurf wrote:
This is one of the areas where the audio magazines *could* help if they so
chose. They could adopt a suitable set of test measurement standards and
apply them. Then both publish the results, and 'name and shame' makers whos
published specs were twaddle.

Alas, the track record is that mags tend to prefer to publish 'subjective
auditions'... Pretty useless for prospective customers, and apply no
pressure on makers whatsoever... :-/

The mags also publish advertisements for the equipment they "review". I wonder
if this could have something to do with the tone of the editorial content?

Rod.