[sdiy] Digital control

[Paul Maddox]

Johannes,

> I'm thinking about building some simple analog FX modules, mainly a
> compressor and a filter. However, I would really like digital control
> over them; at least patch memory. What's the simplest/cheapest way of
> implementing this? I have some experience with PIC programming, so I
> guess what I need help on are some digitally controlled resistors or
> something, to replace the pots.

Maxim do some nice digital potentiometeres, which are serial controlled.
these sounds like what you need.

> Sorry if this is a silly question but I don't know much about analog
> circuitry. I guess I could use digital potentiometer IC's but all I've
> found seem quite expensive and offer very poor resolution. I'm hoping
> there are some DIY circuits.

check out the datasheet for the LM13700 is has a schematic for a voltage
controlled resistor. then its just down to your choice of DAC for the
resoloution.

Paul