[sdiy] LM13700/LM13600-based filters

[David G. Dixon]

> Random observation: the op amp inputs on the highpass and bandpass
> topologies on the 1st page are flipped.
> 
> I only mentioned this since I've done that a whole lot myself, and
> suffered mightily for it. ;)

Yes, I seem to remember something about expensive PC boards ordered with
this error in several places.  Sometimes learning the hard way sucks!

In any case, this is probably the best reason to use simulation software to
draw schematics.  That way, you know your schematic is correct when the
simulation works.