4007 (was: Re: DIY parts)

[Tony Allgood]

JH said:

It's no good idea to have the discharge circuitry of several
VCOs too close together. Your always fighting "interlock",
i.e. a limited minimum beat rate between VCOs, before they
are syncronized (soft sync'ed) thru parasitic coupling.



This is so true. But this weekend I found another example of this sort of
thing in a high level circuit. I had a schmitt trigger CMOS chip squaring
the ramp output of a CEM3340 to give me a square wave. But I could hear it
clicking at the beat frequency with the other VCO. I traced it to the
another gate within the same CMOS chip. This gate was being fired from the
pulse output from the second VCO. Gate to gate crosstalk, and bad enough to
delay the change of state in one of the gates. The problem was solved by
using the gates on opposite quarters of the same chip.

Regards,

Tony Allgood, Cumbria, UK

e-mail: oakley at enterprise.net

Rack mounted Moog VCF module. PCBs have been ordered.

http://aupe.phys.andrews.edu/diy_archive/schematics/effects/filter.html