🚀 go-pugleaf

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    
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