Hi, here's the full circuit for handling signals from your Preamps 1-3.
It uses:-
1 x CD40106,
6 x NPN transistors (2N3904 or similar),
16 x diodes (1N4148 or similar),
1 x DPDT 9V relay,
5 x SPDT 9V relays,
1 x 10uF 25V electrolytic capacitor,
4 x 100nF plastic film capacitors,
2 x 10nF plastic film capacitors,
16 x 27k resistors,
6 x 10k resistors,
3 x 1k resistors,
1 x 100k resistor,
4 x momentary-action switches,
1 x 9V regulated power supply,
Various plugs and sockets,
1 circuit board (Veroboard or custom pcb),
1 metal enclosure.
All resistors are 1/4 W rating.