[sdiy] Modulating a square wave

[jays at aracnet.com]

Justin,

I can't test it out right now but don't think changing the bias would not do much. Maybe if you modulated it pretty fast you might notice it.

Keep in mind that:

1) Most audio stuff is ac coupled. That could get rid of your modulation if it wasn't up in the audio range.
2) 0-50% pw modulation sounds the same as 50-100%.

Have fun.
Jay S.


Justin Owen wrote:

> Hey all,
> 
> I could do with some advice on a particular way of modulating a square-wave.
> 
> A 'standard' square-wave goes up and down between, say, 5 volts (mark) to 0 volts (space). I'd like a square-wave where I had independent control over the voltages/amplitude of (ideally) both the 'mark' and 'space' - so I could have, say, a square-wave that was made up of between 5 volts (mark) and 2 volts (space) or 4 Volts and 1 Volt or 1 Volt and 5 volts - or any other combo.
> 
> So instead of adjusting the width - you're adjusting it's 'height'.
> 
> At this stage it would be for control voltage purposes (e.g. to control the output of a VCA) - so the frequency wouldn't have to be super-fast/high. I'd also be happy with having control over just the 'space' (i.e the part of the square-wave that is normally at 0 Volts) and in a pinch I'd accept 'stepped' control rather than linear if that was going to be much easier.
> 
> I figured I could use a 'normal' square-wave to switch between two different 'reference' voltages (via a CMOS switch or a Multiplexer?) or I could use a comparator and drop the High Voltage and boost the Low one - but I was hoping there might be a simpler/more established way.
> 
> (oh - I posted this earlier today in Rich text - so it didn't go through - apologies if this turns up twice)
> 
> Many thanks,
> 
> Justin
> 
> 
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy