[sdiy] SSM2164 Questions

[Stewart Pye]

I don't have any 2164 chips here yet so I haven't had a chance to 
experiment. Looking at the datasheet I'm having a hard time figuring out 
the control port range/polarity.

The Electrical Characteristics don't tell any more than this:
ground referenced –33 mV/dB control port

and the single supply example states: 0dB gain at Vc = V+/2.

This leads me to believe the following when using a +/-15V supply...
1. There is 0dB of gain when the control port is at 0V.
2. Gain increases 1dB for every 33mV more negative the control voltage 
is (eg -99mV would be +3dB gain)
3. Gain decreases 1dB for every 33mV more positive the control voltage is.
4. The maximum attenuation is quoted as -100dB, so to get this you'd 
need 100 * 33mV = +3.3V
5. The maximum gain is quoted as +20db, so to get this you'd need 20 * 
33mV = -0.66V
6. In normal synthesizer use such as a VCF you'd use an inverting 
summing stage for your CV inputs and add an offset so that with a 0V CV 
input you'd get maximum attenuation (somewhere around +3.3V), and gain 
would increase with increasing CV input voltage.

For those that have played with these chips do these seem like 
reasonable conclusions?


Regards,
Stewart.