Looking for a distortion...

[jalien21]

Okay, so I'm working on this project where I am controling the distortion of a guitar signal by my heart rate. I have an ear clip sensor connected to an arduino, which interfaces with a digital pot, which will control the gain parameter of a pedal. The only issue is that my only digital pot is 10k linear. I could buy different ones, but this is a school project, and i'm running out of time. So my question is this:

I am looking for a overdrive/distortion that has a wide sweepable range from mostly clean to evil on a linear 10k gain pot. Any ideas?

It's possible for me to use my linear pot in place of a log gain pot by using an exponential function to calculate the pot resistance, but I only have 255 steps anyway, so this would probabily result in a drastic loss of resolution.   

[dschwartz]

you can use the pot to control a voltage to the gate of a fet, and use the fet as the variable resistor on the feedback of the opamp..

[blackcorvo]

if you get a LM386, you could build a big daddy/grace, from runoffgroove.com: http://runoffgroove.com/grace.html

they both use a 1k pot but i think 10k would do the trick too. just give it a try, its an easy and simple circuit.

[dschwartz]

yeah, youre right..much easier

or, build any distortion and put the control pot as a volume for the input.

[jalien21]

thanks, dudes! i'll try the 386 circuit as soon as i get home from work- i'm a little skeptical because of the way that the gain pot is in parallel with the internal resistor of the chip, but i have some 386's, and it looks easy enough to throw together, so i'll let you know how it works out.

i'd cook up my own distortion (fet in opamp feedback path sounds like a pretty easy solution- i think i would keep my linear response, too, right?), but i'm still involved in a lot of the other design elements of the effect, for now i just sort of want to drop this into something simple to get it working so i can play with it. later on when i box it up, i might spend some time and design a distortion that sounds totally right.

i like the idea of using it as a volume pot on the input of an existing distortion because it's totally easy. i would expect that you would want to use a logarithmic taper pot, though, right? because it's an amplitude thing?

[CynicalMan]

Your should probably throw some resistors in to reduce the pot to 1k.
According to this, you'd need two 0.5555555555555556kΩ resistors (560Ω).
http://www.diystompboxes.com/analogalchemy/emh/emh.html

[jalien21]

wow! good tool! how have i missed this?

[petemoore]

  The Fuzzpot on a FF is 1k, use/experiment fixed value trim resistors...you probably get a pretty profound effect between say 500ohm and 1k2.
  Use pots where you'd want your fixed resistors to live-evaluate/choose the values.

[boogietube]

The question is...how do you control your heart rate?

[deaconque]

The question is...how do you control your heart rate?

This would be the perfect pedal for a Buddhist monk