> If the amplitude of the signal you are working with is less than about
> 10mV, you can shunt it with a forward biassed diode and pwm (and smooth)
> the supply for the current through the diode.  The attenuation varies a bit
> with temperature etc, but you can get distortion below 5% over a 30 or 40db
> control range.

How would the schematic look like for this idea?