One pot to control 4 points of resistance?

[mike-k]

Hi,
I have a circuit with 4 identical sections. There is a resistor of the same value in each section. I would like to be able to vary that value simultaneously across all 4 sections, using a single potentiometer. Can anyone suggest an approach?

I was originally going to switch between two fixed resistance values and had a plan to use a demux chip in order to introduce an extra parallel resistor in each of the four sections when a switch was toggled. I'm not sure how to introduce continuous variable resistance however.

[themadhippy]

I would like to be able to vary that value simultaneously across all 4 sections, using a single potentiometer. Can anyone suggest an approach?

A 4 gang pot

[mike-k]

Unfortunately space is tight so that isn't an option - I'm using a small pcb mounted pot.

[TimFox]

How close do they have to match?  Could you use 4 LED-CdSe opto isolators (photo resistor output)?  The response time might be a problem, and they have other features including temperature sensitivity.  One source is API, Advanced Photonix, available through Newark.

[mike-k]

Interesting idea - the resistors control the attack time of voices in a synthesizer. Some small variations might actually be interesting, but ideally they would be identical.

[sleemanj]

4 digipots and a microcontroller

[tpowell1830]

quad op amps with unary gain.

[drussell]

I have a circuit with 4 identical sections. There is a resistor of the same value in each section. I would like to be able to vary that value simultaneously across all 4 sections, using a single potentiometer. Can anyone suggest an approach?

Interesting idea - the resistors control the attack time of voices in a synthesizer. Some small variations might actually be interesting, but ideally they would be identical.

What sort of signal are these varying resistances being required to carry?

[Jwillis]

How much restriction to space do you have? There are small 4 gang PCB potentiometers available . PTD904

[mike-k]

Thanks for the suggestions. I will have to do some research into the different options. @Jwillis I probably could fit in these Bourns pots, so that might be the most straightforward option.

@drussell I don't have a schematic for the circuit so I can't provide much detail. It's a 12VDC powered circuit, requiring min 0.4A. There's more info. here: https://somasynths.com/lyra-8-diy/ See 'Tweaks.jpg' in the documentation - this gives a board layout and guide for making mods. I want to modify attack of voices 1 - 4 with one pot and 5 - 8 with another.

[tggzzz]

Use four voltage/current controlled amplifiers, each with the same control voltage/current defined by your your pot.