Hapalochlaena by deadend FX fine control mod

[soldersqueeze]

I'm currently building the Hapalochlaena by deadend FX ( https://drive.google.com/file/d/1Pt4Vf_lv8XeQZaSPm-R03rJ-zvnKOUGY/view ) and want to add a fine pot to the frequency control. I have been thinking that just adding a 1k pot in series to the main frequency pot should do it but I was wondering if anyone would have a glance and let me know if I've underestimated the problem(!) My plan along with the relevant part of the schematic are below.



Does this look like it'd work?
Thanks in advance for any input

[antonis]

I have been thinking that just adding a 1k pot in series to the main frequency pot

Right thought but wrong implementation..

1k pot sould be wired with lug 3 shorted to lug 2 and connectred to 100k pot lug 1..

[Mark Hammer]

On analog synths "coarse" and "fine" controls generally consist of identical pot values, whose wipers feed a common node through lesser (coarse) and greater (fine) resistors; the idea being that they provide control currents/voltages that sum (i.e., coarse dictates "right around HERE" and "fine" is a little more or a little less).

[PRR]

..thinking that just adding a 1k pot in series to the main frequency pot...

Actually (if I read that right), in series with the summing resistor. This will give a 1% change. Which is a lot in pitch, hardly audible in rate (unless you are beating it against a fixed rate). And if you don't like that, you have to get another pot.

Mark's plan, which is older even than Mark<gr&d>, is to duplicate the scheme with a much larger summing resistor. With 100k main resistor, a 1Meg (1000K) 2nd resistor gives a 10% shift; and if you don't like that you can change 12-cent resistors instead of $1.20 pots.

[Mark Hammer]

Thanks for the compliment, Paul! 

[soldersqueeze]

Thank you for all the info, it really helped!
I ended up going with a 10k pot in series with a 100k, which works really well. Good for fine tuning the higher audio range but still usable at the very low lfo range of the pot.
It might have made more sense to use the parallel pot as described by Mark Hammer and kindly drawn out by PRR, so maybe I'll try that on the next one! I just wanted to give some closure to this thread in case anyone stumbles across it in the future.
Thank you again for the help everyone!