[sdiy] LM13700 as VC resistor

Erik Dower electronicpresskit at gmail.com
Sun Feb 9 00:14:27 CET 2020


I’ve used the H11F1 in a few cases and it can work nicely. I seem to remember the minimum resistance not being low enough to fully silence a modular level signal in a series configuration.

I think Doepfer also used it in a filter.

epk

> On Feb 8, 2020, at 7:25 PM, Matti Palm <matti.palm at gmail.com> wrote:
> 
> Feedback modules has made a filter with the h11f1. 
> 
> https://feedback-modules.myshopify.com/collections/diy-kits/products/lpfet-vcf-diy-kit1 <https://feedback-modules.myshopify.com/collections/diy-kits/products/lpfet-vcf-diy-kit1>
> 
> I tried to use it in a mute circuit without luck. I don’t remember why I didn’t like it. 
> /matti
> 
>> 8 feb. 2020 kl. 19:04 skrev music.maker at gte.net:
>> 
>> 
>> 
>> 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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