Digital Encoders with digital potentiometers and save capability?

[RockmanCentral]

Hello, I'm new to the forum but am really enjoying all the pedal PCB's and such.

One project that I've always wanted to try is to copy the preamp section of my Marshall JVM HJS but use one set of digital encoders to control the 4 amp channels and other potentiometers. I think I could get the whole thing into a fairly small enclosure by eliminating the power amp stage and all the redundant controls. IE- it would look like a single channel amp but relays would change the context of the controls, using the same set of encoders for each channel.

I've watched some videos about how to put different pieces together, but nothing that shows all the components needed for a full implementation for each control. IE- the digital encoder, the digital potentiometer, de-bouncing circuit, and how to connect it to an EEPROM to save the data and recall it for a single parameter like volume or what have you. I posted this here because I'm assuming I would need to use an Ardruino to act as the central interface for MIDI, and for controlling all the potentiometers, relays, etc.

Any help/advice is greatly appreciated!!
Thank you!!

 

[Feral Feline]

Welcome to the forum!

Sounds like a cool project.

Alas, it's beyond my scope.

 

[KreoPensas]

I've done some digital pot work.

I have an FV-1 project that uses digital pots, including one to set the rate of the logic chip clock.

Depending on the "usual" things* , you may hear digital noise when *sweeping* because it isn't really sweeping, it's writing a gadload of new positions. Instantaneous jumps ( i.e. recalled setting ) work in a different manner, the output just settles to the new value. They're DAC's in a raincoat. ( maybe three, maybe six )

* usual things being the mitigations applied any time you get high gain circuits and digital toys near each other...
4 encoders with de bouncing? Use an Adafruit encoder seesaw. https://www.adafruit.com/product/5752

The eeprom is probably going to use the same two wires as the above board. So there's that part.

The good digipots are SPI.

I'd use a Teensy 4.0 because you said small.

I'd start with a block diagram of exactly what you want to accomplish.

 

[KreoPensas]

I forgot to mention: I wouldn't consider digital pots to be a "universal" replacement for a real pot in any chosen circuit. There is a fundamental difference in how you're getting to the result.

From a document at digikey:
"the metal wiper of a potentiometer contacts the resistive element with a near-zero contact resistance and usually has a negligible temperature coefficient. In the case of a digipot, however, the wiper is a CMOS element with a modest, but still meaningful resistance on the order of tens of ohms to 1 kΩ. If 1 milliampere (mA) of current goes through a 1 kΩ wiper, the resulting 1-volt drop across the wiper may limit the dynamic range of the output signal."

https://www.digikey.com/en/articles/the-fundamentals-of-digital-potentiometers