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From: brownd@agnes.acc.stolaf.edu (David H. Brown)
Subject: Re: Recording from CD
Message-ID: <1991May2.204418.472@news.stolaf.edu>
Summary: control of output level
Keywords: potentiometer
Sender: news@news.stolaf.edu
Reply-To: brownd@agnes.acc.stolaf.edu ()
Organization: St. Olaf College; Northfield, MN
References: <ERIK.91Apr30190902@zeus.penny.telcom.arizona.edu> <1509@surf.sics.bu.oz.au>
Date: Thu, 2 May 1991 20:44:18 GMT

In article <1509@surf.sics.bu.oz.au> goose@surf.sics.bu.oz.au (Ralph Schwarten) writes:
>[...]
>	The Problem seems to be that you need to be able to control
>	output levels from the cd  Please respond to the net
>Ralph Schwarten
>Bond Uni
>Aus

	Problems of sound quality (8-bit 8KHz CoDec vs 16-bit 44.1KHz CD)
aside, the CoDec does not provide input signal level control. And CD players
often give an unusually "hot" signal, with peaks at around 2VAC p-p;
microphones are invariably much lower. This will result in digital distortion
in a very unpleasant manner (what digital distortion isn't?).

If you wish, you may construct an varible voltage divider from parts commonly
available (say, at a Radio Shack.) In summary, take a variable potentiometer
(resistor) with three pins. For connectors, you'll need a 1/8" mini-phone
plug (into the CoDec input) and an RCA (phono) plug for the CD player--
perhaps two of these for L & R. Wire the center pin of the potentiometer to
the pin of the 1/8" plug. Wire one side pin of the potentiometer to the pin(s)
of the RCA plug(s). The remaining connections are all ground; they should be
connected together: RCA shields (rings), 1/8" sleeve, and the remaining pin
of the potentiometer.

If the volume control seems to work "backwards," either
switch the two side leads on the potentiometer, or live with it and when
anybody asks, just smugly explain that it isn't a volume control... it's an
attenuator, and you're actually increasing the attenuation, not raising the
volume! Either way, it will work.

Email me if you want more information... this is rather terse if you've not
done anything like this before.

Oh, yeah... the potentiometer should be about 100 K-ohms, audio taper if you
can find it, but linear taper is OK, too.

David H. Brown-- Music Department Student Network Representative
brownd@agnes.acc.stolaf.edu	663-2203; office (MWF A.M.) x3363

