[sdiy] LM13700 as VC resistor

music.maker at gte.net music.maker at gte.net
Sat Feb 8 19:01:40 CET 2020



This has been bugging me because I seem to remember a thread here years ago.  I can't
remember what the outcome was, but maybe a search of the archives (for which I seem to have
no foo) might find it.  I do remember it was regarding the datasheet circuits mentioned by
the OP.  Generally, the feel I think was that under the right circuit circumstances, it can
work like a VCresistor.  I remember that the vactrol was compared and is known to work
properly as a floating VCresistor albeit slow to change value.  Not an EE here, but looking
at the floating resistor circuit I see two current producing electrodes posing as a
floating resistor.  I think generally the statement about it's lack of use in synth
circuits is due to it not being very good is probably correct.  Looking at the single ended
circuits, they are AC coupled...

Has anyone experience with H11F1 devices?  Those should be a lot faster than vactrols,
probably more consistent, but I don't know if the transfer function is useful in
audio/synth circuits.

-- ScottG



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