[sdiy] SSM2164 VCAs

[Neil Johnson]

Hi,

Tom Wiltshire wrote: 
> This confused the hell out of me at first too. The examples in the  
> datasheet are very lax about what level the CV should be (Fig 24  
> shows 0-5V CV used). However, the figures are quite clear:
>   -33mV/dB.
> Hence you need 3.3V for fully off -100dB, and -0.66V for 20dB gain.

To be honest, the last thing I'd use the SSM2164 for is a VCA.  Its just too easy, even with the Irwin linearisation.  Unless you want a 4-input audio mixer in which case its an absolute doddle.

It is good for routing/muxing - if you use 0/5V control signal you basically have on/off control (well, ok, "off" = -151dB attenuation, good enough for most applications).

No, to me, the SSM2164 is far more fun for filters, oscillators, and so on.  Got my 18dB/oct filter done, now playing with a VCLFO. Next up 4-pole all-pass filter.  Then perhaps an interesting multi-stage envelope generator.

Or if you want a voicing chip - a single SSM2164 would give you a 2-pole 12dB/oct state-variable VCF with voltage-controllable Q, and a VCA.  Together with an AVR or a (ds)PIC and some sort of DAC you could easily make a MIDI-controlled hybrid monosynth in 2 chips.

Cheers,
Neil
--
http://www.njohnson.co.uk