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From: bill@thd.tv.tek.com (William K. McFadden)
Newsgroups: sci.electronics
Subject: Re: Digital pots (request for info)
Keywords: pots, potentiomemters, audio
Message-ID: <1991May28.231853.6032@tvnews.tv.tek.com>
Date: 28 May 91 23:18:53 GMT
Article-I.D.: tvnews.1991May28.231853.6032
References: <1991May25.232651.11094@leland.Stanford.EDU> <14037@exodus.Eng.Sun.COM>
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Organization: Tektronix TV Products
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You might want to try the LOGDACs from Analog Devices.  They can be
digitally programmed in 0.375 dB steps using an 8-bit control word.
The internal multiplying DAC is 17 bits and is driven by a built-in
decoder.  The attenuation range is 0 to 90 dB.  The part number is
AD7111.

BTW, you can probably do the same thing less expensively using a PCM56
type of 16- or 18-bit DAC and your own lookup table.  You might be able
to get away with an 8- or 12-bit DAC if you can stand bigger steps and
less dynamic range.  For a mixing console, however, you'd better use 16
bits or more.

BTW, for fun a few years ago, I wrote a GW-BASIC program for MS-DOS
that figures out the codes for an N-bit DAC to achieve 2^M
logarithmically spaced steps.  It calculates the required lookup table
plus the error in dB for each step (assuming perfect converter
linearity).  E-mail me if interested.
-- 
Bill McFadden    Tektronix, Inc.  P.O. Box 500  MS 58-639  Beaverton, OR  97077
bill@tv.tv.tek.com, ...!tektronix!tv!bill                 Phone: (503) 627-6920
"Wouldn't it be nice to live in a society where people were more important than
rules and the intent of the law more important than the letter?"