switching at zero cross/noiseless switching

jhaible jhaible at debitel.net
Thu Nov 11 12:19:15 CET 1999


> Nope, you didn't get the question wrong at all - it's just a whacky
> thing to do and I didn't explain my intent well.  At low switching
> frequencies (very sub audio) it is to operate as a basic 4 channel hard
> panner/switch - when it get's a trigger, audio is switched to one of 4
> channels (for signals jumping circularly around the room).  For this
> mode of operation, I would like very quiet switching and could indeed
> live with slow switch times.
>
> But then, I want to be able to sweep the switching frequency up into the
> audio range where YES, there will be all kinds of crazy sidebands and
> general sonic chaos.  Here slow switch times won't work

What about this: Make a crossfade between the two signals (i.e. "slow
switching"), with voltage controlled fade time. Then track the crossfade
speed with the panning LFO rate. If you already have a CV to control the
LFO speed, use this. If not, a simple f->V converter will do.

I vote for the crossfading stuff because when you wait for certain input
conditions (zero crossing, equal values for both inputs) you still
get some artefacts: Even when you have a seamless switching without
discontinuity, the slope of the two signals (d/dt) will not be the same.

JH.





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