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Path: utzoo!linus!decvax!harpo!eagle!mhuxl!houxm!ihnp4!ihuxl!seifert
From: seifert@ihuxl.UUCP
Newsgroups: net.audio
Subject: Re: Power Amp Advice Wanted - (nf)
Message-ID: <725@ihuxl.UUCP>
Date: Fri, 11-Nov-83 10:36:10 EST
Article-I.D.: ihuxl.725
Posted: Fri Nov 11 10:36:10 1983
Date-Received: Sun, 13-Nov-83 04:04:47 EST
References: <2329@hp-pcd.UUCP> <1382@rlgvax.UUCP>
Organization: AT&T Bell Labs, Naperville, Il
Lines: 46

>	On the other side of the coin, I have never had the
>	volume control over 1/2 way, either, so there is still
>	plenty of power with which to shake the walls should I
>	ever get the mind to.  
>	...
>	(b) going back to your stereo shop and having them demo
>	the Polk 10's with a 40, 60, 80, and 100 watt amp, to see
>	just what its requirements are.
>		- Tom Beres
>		{seismo, allegra, mcnc, brl-bmd, gatech}!rlgvax!tom

	I agree with Tom's article, except for a couple of
technical points.  (1) The position of the volume control
(usually) doesn't correspond to what percentage of available
power is being used. That is, having the volume control at
1/2, or "12 o'clock" doesn't mean you are using 50% of the
power amp's available power. It means you are using 50% of
the available voltage gain in the preamp.  What percentage
of available power is being used depends on the output level
of whatever source you're listening to (turntable, tuner, tape,
cd player, etc.), the gain of the preamp (which is what
the volume control controls), and the gain of the power amp.
(some power amps have volume controls)  Some volume controls are
labeled "0-10", these are very misleading. Some are labeled in
dB, which is much better. (for completeness, some are not labeled
at all) The maximum power available (onset of clipping) probably
does *not* occur when the volume control is turned all the way up.
There is usually extra gain (just in case you need it, and to
provide compatibility among various gear), so that clipping
occurs somewhere before 'all the way around'.

Due to the logrithmic(sp?) nature of the human ear, a small
increase in perceived loudness required a large increase
in power. Therefore any difference detected between an
80 Watt amp and a 100 Watt amp is probably mostly due to
increased quality (lower distortion) rather than the slightly
larger amount of available power.

-- 
)
(
 )		from the mildly opinionated keyboard of		
_)__________________	
|OOOOOOOOOOOOOOOOOO|		Dave Seifert
|OOOOOOOOOOOOOOOOOO|		ihnp4!ihuxl!seifert
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