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From: kludge@grissom.larc.nasa.gov ( Scott Dorsey)
Newsgroups: sci.electronics
Subject: Re: Fan for my amp revisited
Message-ID: <1991Apr17.135120.27543@news.larc.nasa.gov>
Date: 17 Apr 91 13:51:20 GMT
References: <1991Apr17.022927.7094@msb.com>
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In article <1991Apr17.022927.7094@msb.com> ritz@msb.com (Chris Mauritz) writes:
>Someone was kind enough to send me a message saying that controlling
>the speed of an AC fan was not as simple as adding a pot.  OK,
>how about I use a DC fan and siphon off power from the power supply
>for the amp?  The power supply seems to be hefty.  Would there
>be any danger that a small DC muffin fan would draw enough current
>to affect the amplifier in any negative way?

   The fan will put noise on the rails of the supply.  Use a seperate
supply for the fan if you can.  Power amp supplies have to deliver a 
large amount of power very quickly in order to track transients, but they
also have to have very low noise to avoid affecting quiet passages.  Power
supply design is the real secret to good sounding amps, and if it works
well, don't touch it.
--scott