Instead of using two types of resistors with 1/2 relation, I just used all the same types, but doubbled one row to maintain the relation. This way you don't need to search for resistors with a proper 1/2 relation, but just can take any resistors, you have at hand. The parallel port connector is not a through hole part, but rather a normal connector, like used in any printer cable. It is quite easy to find and can be directly soldered to the edge of the PCB.

Part Count Remarks

R1..R26 26x 7.5kOhm resistor

C1 1x 0.01uF tantalum capacitor

C2 1x 0.1uF tantalum capacitor

C3 1x 1.0uF tantalum capacitor

C4 1x 1.0uF electrolytic capacitor

SW1 1x Quad-Switch (like LCSC C559139)

AUDIO1 1x 3,5mm Audio jack port (like LCSC C145816)

LPT 1x DB25 parallel port M-plug

Project by Necroware