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From: "Phil Allison"
Subject: Re: low distortion oscillator
X-Newsreader: Microsoft Outlook Express 5.50.4522.1200
Date: Sat, 9 Nov 2002 20:12:06 +1100
NNTP-Posting-Date: Sat, 09 Nov 2002 20:02:22 EST
Organization: Telstra BigPond Internet Services (http://www.bigpond.com)
"MIKE CONNELL" wrote in message
> There is a schematic for a cheap low distortion oscillator based on
> a Wein bridge. It is page 30 figure 40 in
> The distortion is below .003% which is pretty good compared to
> available units.
** It is much higher at low frequencies due to use of lamp/s as
> The problem with this circuit as I see it is the dual ganged potentiometer
> that has to have each section matched to within .1%. All the other parts
> Is such a potentiometer with this tight matching actually exist?
** A pair of multi- turn WW pots would get close.
I'd> appreciate> any pointers. I know it could be done with fixed resistors,
but like the
> idea of infinite adjust.
** Forget dual carbon pots, they have bad contact noise and distortion,
large setting drift and a poor temp co-efficient. Maybe a dual plastic track
would do but the multi turn WW is far the best.
There was an item in Electronics World recently about ganging a pair
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