Morgans: Thank you for the reply. The digital potentiometer is a good idea. It's interesting, and will solve the issue of that filthy noise interference I seem to get when turning the pots. I'm familiar with opto isolation chips, so I will explore this option.
Regarding the pwm output, and smoothing. Would this be digital / analog conversion? Unfortunately, I do not own or know how to use an oscillioscope yet, so I can't get a good clear understanding of what type of signal, voltage and current is running through the circuit I'm trying to manipulate. I am still getting headaches studying the math needed to divide resistors, using capacitors - which wouldn't matter anyway since I have no scope to test my work. I wish I could find a useful oscilloscope I could afford.
I haven't used a Teensy or Due yet, they are on my list of things to buy & try.