Using potentiometer in two separate circuits
What you are proposing is very unlikely to work. Your micro-controller ADC (analogue to digital converter) input is expecting a signal in the range 0 to +5 V. For a potentiometer input this will be wired as shown in Figure 2.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. A potentiometer connected to a micro-controller ADC input.

A guitar amplifier, on the other hand, consists of an AC signal pre-amplifier with tone and volume controls feeding into the main amplifier stage. The guitar signal with high-output pickup at full volume might put out a signal of +/-1 V peak. You can't have this voltage on the potentiometers at the same time as using it for a 0 to 5 V signal.

In the example shown the op-amp is fed from a single-ended supply. We know this because there is a ground symbol on the negative supply pin and a positive connection on the other. The DC+ is likely to be in the range of 12 to 18 V. To allow the output to swing positive and negative we need to bias the output to mid-supply. That's the purpose of R5 and R6. So on a 12 V system the quiescent voltage on the output would be 6 V. Since this is fed back to the potentiometers you can see that the voltages on the pots will be about 6 V with the guitar signal superimposed on it.



Figure 2. A Baxandall tone control stage typical of many guitar amplifier pre-amp stages. Source: Learn About Electronics.