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I am trying to find a 1k linear digital pot which has a very low (preferably 0) wiper resistance. Any interface would be ok (apart from just up/down).

I found this article: http://electronicdesign.com/components/active-cancellation-pots-wiper- resistance which could be a way around the issue.

What I am trying to do, is substitute the 1k pot in the classic fuzz circuit

http://www.geofex.com/article_folders/fuzzface/fftech.htm

with a digitally controlled one, and it needs to pretty much go down to 0 Ohm to get the full fuzz effect. I am not sure if the above 'trick' may interfere the fuzz's simple circuit which is extremely sensitive.

Does anyone have any suggestions, feedback or alternative idea?

Thanks!

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  • \$\begingroup\$ You do know that "real" potentiometers also have non-zero wiper resistance, right? \$\endgroup\$
    – Connor Wolf
    Commented Mar 11, 2015 at 1:44
  • \$\begingroup\$ yes but they tend to be quite low. around 1-2 Ohm or less. All the digital ones I've seen seem to be at least 50+ Ohm. I would be fine with 1-2 even 5 ohms... \$\endgroup\$
    – Guy Taylor
    Commented Mar 11, 2015 at 2:11
  • \$\begingroup\$ How much resolution do you need? What step size? How many steps? \$\endgroup\$
    – Dwayne Reid
    Commented Mar 11, 2015 at 3:23
  • \$\begingroup\$ I was hoping for 128 steps, which would map nicely to MIDI controller messages. \$\endgroup\$
    – Guy Taylor
    Commented Mar 11, 2015 at 9:43

1 Answer 1

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You will likely not find such a part because there will always be some kind of electrical switch in a digital potentiometer, and these always have some built-in resistance.

You can however compensate the resistance. You've already linked one article that shows it, but you can improve upon that.

A single OpAmp and three resistors can work as a negative resistor. If you tune the negative resistance to your wiper resistance you end up with near perfect compensation.

Wikipedia Article on Negative Impendance Converters

For your application there is even a article on the web that does exactly what you need:

Negative Resistance Nulls Potentiometer's Wiper Resistance

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