Part="AudioJack2"> Quad operational amplifier, DIP-14 A-1135 2 8 pin DIP socket A-004 4 Knobs Screws, nuts, and spacers (see build notes The build is pretty straightforward except for mechanical assembly, and one 16-pin IC. But 3 panel-mounted UI elements for every step (plus some others), so plenty of room for a press-on type knob (rather than using a setscrew). (ShaftLength must be non-zero. ShaftDiameter = 10; label_font = 6; //knob_radius.