[sdiy] Temperature Compensated Exponential ConverterUsingSSM2164

[Magnus Danielson]

George Hearn wrote:
> Slight change of tac but...
> 
> The CEM3374 (Oberheim Matrix 12 / Xpander etc.) almost completely
> obliterated temperature drift in by providing a 3300ppm/k dependant voltage
> on a pin.  If this voltage was used to derive the DAC reference (multiplying
> DAC) that drove the VCO then almost perfect temperature compensation is
> achieved.
> The drawback is of course that all your modulation sources must then be
> digital since the input to the multiplying DAC is of course a binary code.

Actually, that's not entierly true. Modulation source scaling isn't 
particularly important as long as they don't shift frequency permanently 
or for longer times. So LFOs just need to avoid producing DC levels and 
you are home free. ADSR scaling may be of importance if you want to hit 
certain notes during modulation, but other than that... no.

Cheers,
Magnus