AW: LM13700 VCF update no.2

[Haible Juergen]

	>Sounds like it would be better to build a Moog ladder then.
Would this
	>be better alternative to the state variable design.? 

Very different stuff. Always good to have one of each filter.
You'll have a hart time to build the moog without trimmpots.

	>And I'm not quite sure that input offsets would cause the
breakthrough
	>that I'm seeing here. 

What else than offset voltages should cause this behaviour??
(If you have a 13600, that's completely different stuff, btw !!
But the '700 only modulates the amplifier bias current.)

Have you measured the external voltage between the input pins?
There's still an internal offset voltage of some 5mV or so,
but when you use the linearizing diodes (why do you want these
at all, btw?), chances are that you introduce a much larger amount of
external offset voltage. I don't know the very circuit you use,
but these single-chip 13700 state variable filters mostly use DC 
coupling from the darlington buffer to the ota inputs - imagine
what errors this will cause with temperature changes !

JH.