Filter ICs and crossfade circuits

[Michael Potas]

Does the dual VCAs require a linear or log taper?  You would want the output amplitude to be close to constant (assuming the two input waveforms are of the same amplitude) when fading from one side to another, so you dont hear the volume drop or peak in the middle of the crossfade.

Cheers,

Michael   
 




Yeah.. I actually want to do a QUAD VC-crossfade circuit, with the audio 
inputs amplitude controlled by default with a joystick. When C/V is
inserted, it bypasses the voltage output by the joystick. This would be in
my mind beautiful for mixing, say, HP/NP/LP or saw/tri/pulse/sine outputs.
I forget who I was discussing mixing waveforms with a few months ago, but
I was trying to argue that it's better to have just output jacks and no
mixing ability.. was I ever wrong... 

For a dual crossfade, just run the second VCA through an inverting opamp
at unity gain. Should work dandy as long as you trim the C/V on both of
them correctly. You could always use the dual-opamp + 3080 method, but
it's a little noisy IMO. Definitely usable tho! 

Andrew

-| Andrew Schrock | aschrock at cs.brandeis.edu |-