[sdiy] XOR as 'digital' ring modulator

[Colin f]

> > You can't modulate the polarity without modulating the amplitude.
> > The polarity is the sign of the amplitude.
> 
> Yes, and therefore you are modulating the "sign" and not the 
> "amplitude".

Well if we want to get pedantic about it, when you invert the sign of a
square wave with anything other than a perfect duty cycle of 50%, you shift
the DC level, so you would change the RMS amplitude.
Depends on which definition of amplitude you're using.
But I know what you mean.

Cheers,
Colin f