Feedback device [subtle signal divider and or current limiter]
A very simple passive way to add control to a no input mixer setup without disturbing the purity of the instrument.
Attenuation in an audio mixers is via voltage dividers (which shunt energy to ground) oscillation tends toward tight/short sequences. A 50k logarithmic potentiometer wired as a variable resistance (current limiter) is a fine tuning device and a way to loosen up sequences and extend there complexity over time.
Switching jacks allows this box to have multiple uses. it is 2 x 1 to 2 splitter or a 4x passive current limiter
