eacj@batcomputer.tn.cornell.edu (Julian Vrieslander) (10/04/89)
Some time ago there was a discussion in this group on how to implement a
digitally controlled attenuator. I put in a plug for the Analog Devices
AD7111, a logarithmic D/A convertor that attenuates an analog input signal
over the range 0 to -88.5 dB, according to a value latched into an 8-bit
data word.
But now I find that I need to build a digitally controlled attenuator with
a range of 0 to -120 dB! I thought of cascading 2 AD7111's, but it looks
like the noise specs are not good enough. The best alternative that I
have found is the MTA1537 Voltage Controlled AGC/Attenuator from VCA
Associates (Canoga Park, CA). This is a low noise, low distortion IC
optimized for HiFi gain control applications. Controlling it digitally
will require an D/A stage to supply the control voltage.
If anyone knows of equivalents or alternatives to the MTA1537, I would
appreciate hearing about them. The input signal will be 7 Vrms, with 10 Hz
to 10 kHz bandwidth.
--
Julian Vrieslander
Neurobiology & Behavior, W250 Mudd Hall, Cornell University, Ithaca NY 14853
UUCP: {cmcl2,decvax,rochester,uw-beaver}!cornell!batcomputer!eacj
INTERNET: eacj@tcgould.tn.cornell.edu BITNET: eacj@CRNLTHRYgregb@hplsla.HP.COM (Greg Branson) (10/05/89)
You might want to try dbx in Sunnyvale, CA. They make VCA's for automated recording studio mixing consoles. They will probably be best available. I'm sorry, I don't know the specs. The very expensive automated mixing consoles use digitally controlled motorized faders. One of the manufacturers is George Massenburg Labs (possibly known as GML, Inc.) located in the Los Angeles area. Greg Branson gregb%hplsla@hplabs.hp.com