Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!uwm.edu!csd4.csd.uwm.edu!info-high-audio-request
From: miker@polari.UUCP (Mike Ranta)
Newsgroups: rec.audio.high-end
Subject: Re: Need power regulator recommendations
Message-ID: <13500@uwm.edu>
Date: 27 Jun 91 12:54:47 GMT
Sender: news@uwm.edu
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Approved: tjk@csd4.csd.uwm.edu
Originator: tjk@csd4.csd.uwm.edu


In article <13454@uwm.edu> bms89@ecs.soton.ac.uk (Scally BM) writes:
>
> I'm about to ramble again.....

(good stuff deleted...)

> Thus in a well built amplifier there will be devices to remove the
>HF noise thus preventing it from causing distortion to the signals.
>
> Due to cost cutting pre transformer hf filters, and post transformer
>bypass filters are often left out.

Power amps usually have at least an RFI supression capacitor on the
secondary of the power transformer.  The transformer itself also provides
a great deal of attenuation.

> Consider the specifications though..
>
> This devige has to 'repell' noise down to 7K (at low levels
> at the bottom frequency) yet be capable of responding to
>current transients at up to 20K. Hummm
>
> A tad of a design problem I fancy.

This is not the case.  The filter capacitors in an amplifier cause the
input current to be very low frequency.  If you put a small value
resistor in series with the AC line and monitor the current waveform
with a scope (watch out for common mode voltage) you will see a very
low frequency waveform (typically far less than 100 hz).  We're talking
about orders of magnitude here which makes filtering an easy task.

> Any help will of course benafit the sound but to much control
>will strangle the life out of the system.

This is not true.  While RF junk on the line can certainly cause audibile
side effects, the filters themselves, unless they inhibit current at a
few hundred hertz (which would take a HUGE inductor) do not create any
problems of their own.
>
(More stuff deleted...)

> A device that filters and rectifies the mains and then
>modulates it at a constant frequency (50/60hz) with
>enough power to run an amplifier (or two..) you are right
>this is getting silly. Such devices are available..
>for turntables as well...

This would be powering an amplifier from essentially another
amplifier--your're right, that is silly.

The moral of all this remains the same:  A good RFI filter and surge
supressor between all of your audio equipment and the wall is a good
investement and certainly can't hurt.  A dedicated circuit for your
system may also be of benefit.  Anything else, however, is either
unnecessary or possibly even detrimental.