BD and SD Decay can be set with 2K2 log potentiometers. It is very important to add a 300Ohm resistor to it, to avoid a continuous decay, that never stops!
HH and SD-Noise Decay are set by a two way switch that has no connection on middle position and a 5MOhm and 20MOhm on the outer positions. While the resistor value needs to be very high to get acceptable decay modifications, i decided to use switches. The switches have no connection when set to center position, so the original decay value is still available. With both outer positions of the switch shorter decay values are possible.
If you try it at home, don't blame me if you mess it up and your monotribe gets damaged.
When using log potentiometers you need to ensure that you use the correct side of the potentiometers for the BD/SD Dacays so that you have a wide control range where you can set the decay relatively precise.