[sdiy] LM13600 Gain Question

[jhaible]

> Oh, that standard offset-trimming pot is a seriously bad way of doing it.
> Reason? When adjusting it for input offset correction, you also changes
the
> gain of the input-damping and thus of the whole curcuit.

True - although the gain only changes very little.
Why? Because the "shunt" part of the input voltage divider is mainly
formed by the linearisation diodes (!), and only to a lesser degree by
the offset trimmer. So you probably won't notice much gain
variation due to offset adjustment in an ordinary VCA.
BUT - and here Magnus' point strikes with full force - if you
build a Ring Modulator, or any other circuit where a direct path
and VCA's path must perfectly cancel for a certain CV level,
this can indeed be quite troublesome.

JH.





>
> > Bottom line for me means rough calcs and throwing it on the SBB to fine
it
> > out.
> >
> > Thanks guys, this is what I needed.
>
> Well, that is what Synth-DIY is about - sharing info!
>
> Cheers,
> Magnus
>