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I have an analog sound processor unit, which uses either ICs or spare components.

There are four controls, which are simple potentiometers. I would like to control their levels digitally, storing the settings in an EEPROM.

Which are the architectural most advisable solutions?

The idea is to transform an analog device into a MIDI controlled device, I am available in doing it with more elementary components or, if possibile, implementing ICs which can do the job.

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closed as too broad by winny, laptop2d, evildemonic, Dmitry Grigoryev, Warren Hill May 29 at 9:35

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I've done a nearly identical project as a one-off for a customer in the past.

Motorised Potentiometers exist (ALPS is one manufacturer), but the response speed is slow, so that may not be suitable for your application.

Digital Potentiometers are available from multiple manufacturers and are generally SPI/I2C controllable, which are both easy to interface to your controller of choice.

Digipots do have a couple of serious limitations that need to be considered for this sort of project.

They have a maximum voltage window between different terminals (usually, but not always, the device supply voltage) and requirements for the ground reference. This may or may not be a problem depending on how your existing device uses the potentiometers. For my device the maximum voltage differential was within the acceptable range, but the ground reference was not suitable. So, I used a small isolated DC-DC converter (e.g. XPPower), and a isolating-coupler (e.g. TI iCoupler) to allow a Digital Potentiometer (e.g. Microchip) to be placed on each channel while staying within the device limitations. A low-cost microcontroller drove each channel via SPI.

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    \$\begingroup\$ It should also be mentioned that there are also digital potentiometer ICs that already have an integrated EEPROM. \$\endgroup\$ – Sim Son May 13 at 11:12
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You'll need a microcontroller to "speak" to your digital interface (e.g. MIDI). Such microcontrollers typically come with internal non-volatile memory, so that solves your "how do I store the settings" problem.

There's digital potentiometers, which you can talk to from your microcontroller.

If you don't want to modify the original analog circuit, you could use a servo/motor to turn the knob of a potentiometer, albeit that would be a pretty complex task and pretty expensive.

If these potentiometers are used to set the gain in an amplifier (that's their most common use): There's also Programmable Gain Amplifiers that can be had for cheap as drop-in replacement for an amplifier circuit.

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You probably want an audio-taper digital pot like the ds1882

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