[sdiy] Coarse and Fine Pots

[Roman Sowa]

You can modify the LFO to change it from tuning resistor into tuning 
divider. Feed the output of Schmitt to a pot wired as divider with 2nd 
tap tied to the reference point of the integrator, and then a resistor 
from the wiper to integrator's input.

Roman

W dniu 2025-05-25 o 19:02, Terry Bowman via Synth-diy pisze:
> 
>> On May 24, 2025, at 9:34 PM, Michael E Caloroso 
>> <mec.forumreader at gmail.com <mailto:mec.forumreader at gmail.com>> wrote:
>>
>> Just sum the CVs from both pots to the CV summer opamp, configure the 
>> fine tune pot to lower gain.
> 
> It's the frequency pot for a Schmitt trigger/integrator LFO. I'd love to 
> have some VCLFOs but that isn't in the cards. I'd love to build a 
> modular version of this thing but I don't have the cash.
> 
> A dual concentric pot would be convenient and cool but it's not a 
> deal-breaker. I saw a 100kΩ / 20kΩ somewhere but it was out of stock, 
> probably for a long time.
> 
> 
>> On May 24, 2025, at 11:29 PM, Ben Bradley via Synth-diy 
>> <synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org>> wrote:
>>
>> It's been quite a while since I've touched an SEM, but yeah, I think
>> those are two separate knobs on a reduction system that goes to the
>> shaft of one pot. These were used on the tuning shafts of old radios
>> from many decades ago. It's usually a ball bearing reduction and they
>> appear to be rather expensive.
> 
> I had a Two-Voice and I loved it. No stops on the fine pot, what a concept.
> 
> I hadn't found any for sale up until now so thanks for that. Are the 
> knobs twice as much?
> 
> 
> Terry Bowman, KA4HJH
> "The Mac Doctor"
> 
> https://www.astarcloseup.com <https://www.astarcloseup.com>
> 
> “...the book said something astonishing, a very big thought. The stars, 
> it said, were suns but very far away. The Sun was a star but close 
> up.”—Carl Sagan, "The Backbone Of Night",/Cosmos/, 1980
> 
> 
> 
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