[sdiy] XOR as 'digital' ring modulator

[Colin f]

> I think that if you are willing to use only square or pulse 
> waves, the "x-or" gate is a true multiplier, therefore it 
> ~is~ a ring modulator.
> 
> An analog ring modulator is capable of handling both the 
> signal inversion (or not) and amplitude variations.

The problem with the XOR ring-mod is that two ring-modulated square waves
produce an awful lot of over-tones.
For very little extra parts count, you can build a ring-mod with one input
that is square wave-only, but another than can take any waveform.
That would be a switchable inverting/non-inverting buffer.
Ring-modding a square wave with a triangle or sawtooth waves gives a rather
more useful choice of sounds than pure square waves only.

Cheers,
Colin f