Spring-loaded controller knobs (bcr 2000 mod?)

knobs that return to their original position such as the pitch bend wheel...

i've been toying with the idea of this for a long time, i really need these for tweaking effects and live use

does anyone know about these things? i've been thinking about modding my bcr-2000 so that one line of knobs always return...not really into geeking and soldering about with these things

now the problem would be how to determine the center...knobs on many keyboards are endless rotary controllers...

how a bout a combined LP/HF filter that would bring the cutoff down when turned left and same thing on the right

i know its not the same but you can set a button as an on/off switch for the filter then when (in the case of a high pass) you reach where you wanna go, you just hit the button and the fx turns off bringing you back to the original sound.