expression pedal to a dual ganged pot (ie Super Tone Control)

[dustin]

Hi everyone, I'm a bit of a newbie but have been doing a lot of research.  I'm trying to modify the Craig Anderton Super Tone Control to accept a standard expression pedal or CV for the frequency.  The concept seems simple enough for a single pot but the STC's frequency control uses a dual ganged 10k pot.  I've read about using an LED/LDR and it seems like you could hook up two of these and get control of a dual ganged pot like I need.  I've tried with a VTL5C4 but only get about 1k of resistance.  I thought I could just use the EMH linear pot calculator to up the resistance to 10k but it looks like those values are out of range for the calculator.  All and all I'm beginning to think I'm going down the wrong path.  Maybe I just need a different vactrol or maybe there is a better way to do this all together?  Any suggestions would be helpful.  I'm trying to avoid building a custom expression pedal for this project.  Thanks. 

Dustin


PS
Also does anyone know about adding CV (modular synth style) to a pedal.  I've noticed on a few other pedals that if you can hook up a standard expression pedal than you can hook up CV.  I'm not worried about scale of the cutoff frequency or anything like that, it would just be cool if I could hook it up to an old CV sequencer.  It seems like it could work just want to make sure I'm not missing something. 

[dustin]

anyone have any ideas on this?...      racking my brain.  I'm pretty new to all of this so hopefully there's a simple solution I'm missing maybe some sort of IC that can measure resistance and resist at the same value??  idk...  I've also thought about making a new pedal with a dual ganged pot but it would need a multi pin cable maybe a MIDI cable or something to connect to the pedal. 

I guess if I had a decent enclosure with a pedal (like the Digitech Whammy pedal) it would be simple to do it all internally. 

damn.... anyone have any ideas???

[Processaurus]

Did you see this?

http://www.thetonegod.com/tech/rockncontrol/rock.html

[smallbearelec]

Here's a How-To that may useful:

http://www.smallbearelec.com/HowTos/Swell/Swell.htm

Regards
SD

[dustin]

Thanks guys!!     I had seen a geofex article but it only alluded that it was possible but did elaborate at all.  http://www.geofex.com/Article_Folders/xprnped.htm  The tonegod rock n' control article is great!!  I'm going to order some optocouplers and see if I can't get it working.  Thanks!!   

[Mark Hammer]

I used to have a Super Tone Control mounted in a foot pedal, and physically swept the dual-ganged pot with the foot treadle.  The circuit used the mod described here on page 13:  http://hammer.ampage.org/files/Device1-8.PDF .  Great pedal, particularly if one can include a switch to flip the hot and ground connections of the pot to permit reverse sweep.  The bandpass and lowpass settings don't benefit from that mod quite as much as the highpass setting, where sweeping the foot treadle forward essentially "guts" the signal by filtering out lows and mids.  I found that flipping the direction of sweep in highpass and notch modes often made it easier to translate my mental goals for tone into appropriate forward and backward motions.