LM13600/700 as VCA... square wave troubles.

[ExpAnonColin]

My max freq has been trimmed down to 12.5hz, which is still fairly fast.  I'm using a .1uf cap now...  If the trap wave is shifted up a little, it stops popping.  I can get the square entirely nulled.  The problem is that the square wave now swings from 2V to about 8.5V, while the triangle only goes from 2 to about 6.5...

Perhaps shift the op-amp a little higher and use a larger resistor for Iabc?  This might allow you to adjust things for a steeper slope/higher frequency. 

This is why I prefer the OTA approach I outlined in that thread.  You can set a very definite upper threshold.  Anyway, you're on the right track by the sound of things.  Stick with it and keep experimenting.

PS  I managed to do this and without the need for a nulling pot, so it's doable.

That's what I was talking about in my post-by series resistance.  I'm still not entirely satisfied.  I'll keep futzing around.  Thanks a bunch for all of your help.

-Coiln

[puretube]

I see some (lots of..) future foreheadslappers in my imaginary eyes 

:icon_mrgreen: