simple crossfade circuit???

[List, Christopher]

There is a simple way for linear x-fades (not perfect for audio signals
as the volume is a little low at 50% mix but it'll work)... 

Run your two signals to either end of a 100k linear taper pot. Connect
the wiper of the pot to an op-amp setup as a simple voltage follower.
That's it. Note that if your signal sources have a very high output
impedence, you won't get a complete x-fade. 

I use this trick with all of my state-variable filters to get a Lp to Hp
x-fade output. For the ASM-1, I use the op-amp that buffers the notch
filter output as my voltage follower, as a 50% LP/HP x-fade is the same
as the notch filter output. You hardly need to modify the PCB for
this...  

The kind of audio + inverse audio dual x-fade pots you're looking for do
exist. The 12mm PCB mount Panasonic pots in the Digikey catalog with
"AC" taper are set up that way. For better or worse, those ones all have
center-detents.

- CList


> -----Original Message-----
> From:	dan mcmullen [SMTP:dog at well.com]
> Sent:	Wednesday, June 03, 1998 11:20 AM
> To:	synth-diy at mailhost.bpa.nl
> Subject:	simple crossfade circuit???
> 
> hello all,
> 
> i need to crossfade between two signal sources using a fader type pot.
> is
> there any way to do this other than using a dual pot with inverse
> audio
> tapers on the 2 paths?  do such things even exist?
> 
> many newbie thanks in advance,
> dan
> ___
> dan mcmullen, sf, ca, usa                  don't worry - pay attention
> mailto:dog at well.com                                       415.681-0712
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