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From: rcd@opus.UUCP (Dick Dunn)
Newsgroups: net.audio
Subject: Re: Phil R.'s system, part3 (power mains)
Message-ID: <787@opus.UUCP>
Date: Mon, 10-Sep-84 23:30:26 EDT
Article-I.D.: opus.787
Posted: Mon Sep 10 23:30:26 1984
Date-Received: Fri, 14-Sep-84 07:32:39 EDT
References: <1010@drutx.UUCP>
Organization: NBI, Boulder
Lines: 40

> Mains:
> 
> All 60Hz 120VRMS power is RF filtered and capable of supplying more than
> twice the peak current demands of all components combined.  The power
> amplifier is on its own dedicated 30A RF filtered line that also
> incorporates a remote soft start circuit.

One serious observation:  Why is the soft start circuit on the amp?  And why
is it on a separate circuit?  That looks to me to be a double invitation to
trouble.  You should have the whole mess controlled at the preamp:  The
power for the amp should be switched at the preamp, so that if you lose
power at the preamp or one of your sources (which should share supply), the
preamp can attempt a graceful shutdown and HOLD things down until you give
it the go-ahead.  If you don't do this, a power glitch can shut down the
input side, while the amp's monster power supply hangs in there (no signal
to drain it) and rides right over the glitch.  The source comes back after
the glitch with a resounding click containing all known frequencies--and
the amp interprets this as a request to embed as many speaker cones as
possible in the far wall of your listening room.

Now for fun--gee kids, I hope that most systems have the rest of what
Phil's does, without even trying too hard: My amp (100W/CH) only
needs 370 VA max, and it's the hungriest part of the entire system.  I doubt
seriously that I can get the system to snarf down more than 600 VA even if
I'm making both open-reel and cassette copies of a disc while playing at
max power.  My system is on a standard 15-amp breaker, and I know that it's
possible to suck pretty close to twice the rated capacity of the breaker
for a short time (=="peak demand").  So much for current capability.

As for RF filtering, I just went through and peeked.  Every one of my
components has a power supply that starts with a power transformer.  No, we
don't run the circuitry in our amp or preamp or anything else on 120V AC,
do we?  Nosiree!  The filtering?  Oh, have you ever tried to pass RF
through a transformer designed for 60 Hz?  Even if you manage to get a few
picovolts through, you've got all those nice big filter capacitors on the
other side of the transformer to cut it down even more.  The power line
just ain't where the RF comes in.
-- 
Dick Dunn	{hao,ucbvax,allegra}!nbires!rcd		(303)444-5710 x3086
   ...Keep your day job 'til your night job pays.