On Sun, 25 Jun 2006 20:01:55 GMT, "Arfa Daily"
wrote:

It was just for interest then that I asked the question about whether 'real'
meters read the power in the whole wave, or just one half. So when an amp
says its output is 50w RMS, setting aside all the debate about whether RMS
is valid, just taking it to mean what we all know the manufacturers want us
understand by that, is it 100 watts of power contained in one half cycle, or
one whole cycle. I'm sure you all know what I mean - I'm just not putting it
very well ...

Yup. "Real" audio power meters have an interesting design where the
permanent magnet in the meter is replaced by a coil, which carries the
same current as the movement. The result is that whichever way the
current flows, it sends the needle upwards, so the meter naturally
rectifies without diodes. Also, the deflection varies as the square of
the current, so it is automatically linear on a power scale.

d

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Pearce Consulting
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