AW: Re: Serge-style CV inputs

Haible_Juergen#Tel2743 HJ2743 at denbgm3xm.scnn1.msmgate.m30x.nbg.scn.de
Thu Mar 14 22:35:00 CET 1996


> Sounds like what you really want is a "sign changer", which looks like 
this:


                          |-/\/\/\-|
                          |        |
                          | |\     |
           in -+-/\/\/\---+-|-\    |
               |            |  \   |
               |            |  /---+-- out
               \            |+/
               /<-----------|/
               \
               /
               |
              ---
               -

That's my favorite way to do it, too. Only one opamp required, and
high input impedance, low output impedance at the same time.
I often use pots with center stop. To achieve exactly zero gain
at the center stop, I usually solder a trimpot parallel to the normal
ptentiometer, with approx. 10 times its value.
The trimpot also prevents lock-up in case of intermittent
work of the main pot.
Good values are 100k for resistors and pot, and 1M for the optional
trimpot.

JH.



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