masaki@elaine13.Stanford.EDU (Pixel) (05/26/91)
I seem to recall that a few months back, digital volume controls were discussed in this newsgroup. I'm sorry if this is bringing up a dead subject, but does anyone know a company that makes or sells digitally controllable potentiometers which are of suitable quality for high quality audio production. (I'm designing part of a sound mixing console.) Thanks for any help you can give me. .....,,....,.. Albert Huntington | Any government will work if ....,.,....,.. masaki@leland.stanford.edu | authority and responsibility ...,..,....,.. (415) 497-6327 | are equal and coordinate... ..,,,,,,,,,,.. /~~~\ Stanford University | .,....,....,.. ( ^,^ ) doesn't even know | Lazarus Long (R.A. Heinlein) ,.....,....,.. \_~_/ or care about this. | _Time Enough For Love_
bender@oobleck.Eng.Sun.COM (memory fault - core dumped) (05/27/91)
In article <1991May25.232651.11094@leland.Stanford.EDU> masaki@elaine13.Stanford.EDU (Pixel) writes:
->
-> I seem to recall that a few months back, digital volume controls were
->discussed in this newsgroup. I'm sorry if this is bringing up a dead
->subject, but does anyone know a company that makes or sells digitally
->controllable potentiometers which are of suitable quality for high
->quality audio production. (I'm designing part of a sound mixing console.)
I was reading an issue of EDN the other day, and noticed an ad for digital
pots from Dallas Semiconductor (I hope that's who it is). Anyway, I think
they had several versions (i.e. number of steps and resistances) but the
neat thing that the ad mentioned was they they could be used as drop-in
replacements for a regular pot (or trimmer), AND they retained their setting
even when power was removed (just like a real pot/trimmer).
You might give them a call; they also make other kinds of neat stuff; their
forte seems to be lithium-battery-backed-up everything, and they also make
those clock-in-a-ROM-socket things.
mike
--
Won't look like rain, Won't look like snow, | DOD #000007
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We just can't tell you anymore, We've never made oobleck before! | MSC #298726kludge@grissom.larc.nasa.gov ( Scott Dorsey) (05/28/91)
In article <1991May25.232651.11094@leland.Stanford.EDU> masaki@elaine13.Stanford.EDU (Pixel) writes: > I seem to recall that a few months back, digital volume controls were >discussed in this newsgroup. I'm sorry if this is bringing up a dead >subject, but does anyone know a company that makes or sells digitally >controllable potentiometers which are of suitable quality for high >quality audio production. (I'm designing part of a sound mixing console.) > Thanks for any help you can give me. I, as resident audio fanatic, suggest not using the CMOS volume control circuits which are so ubiquitous in consumer audio gear, because, quite frankly, they sound bad. Your best bet for quality is to use an 8-bit D/A and use the output to drive an OTA. The National Semi transconductance amps are probably your best bet. Still, you'll get lower noise from a mechanical stepped attenuator :-). --scott
bill@thd.tv.tek.com (William K. McFadden) (05/29/91)
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?"