[sdiy] CV mixer help

[Jim Patchell]

    What you need to use is a summing amplifier.  You can find a 4 input example
on page 18 of http://www.silcom.com/~patchell/smb1/smb.pdf on the left hand side
of the schematic (the right hand side has a bunch of voltage to current
converters).  I use 1 meg resistors for the summing inputs to keep the input
impeadence up.  The examples I have also invert the inputs.  You will need to
add another inverter on the output if you want a positive output for positive
inputs.  Hope this helps.

    -Jim

pelagius pelagius wrote:

>   I've been trying to build a simple 8 channel cv mixer to use as a
> sequencer expander for an 8 step trigger sequencer (made by an unmentionable
> manufacturer ; )
>   I currently have 8 pots going into two opamps (I just copied the output
> section of the superseq schemo).  The problem I'm having is that turning
> each pot affects all of the others.  I'm wondering if anyone knows what may
> be causing this.
>   Or if anyone knows of a good simple schematic I could use to build an 8
> channel cv mixer, I'd be willing to start over.
>   Thanks
>
> P.S.  Also wondering if anyone knows of a good schematic for a vc switch
> that works.  I'm afraid to bother with the one in the Terence Thomas book,
> and I can't find any on the web.  Is that a difficult circuit, or just too
> boring for most people to bother with?
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