What we need
The label of the logical IC's are some different by the different
companys. But at all: there is a international standard. The last 4
numers in the label are the same everywhere.
The IC "4052"
we need :
You can see: the last 4 numbers are the same.
Don't use the 74... types (example 74HC4052).
1x 4052 (4 channel Multiplexer/Demultiplexer)
1x MAX238 (in 24-DIL package) (RS232<->TTL transceiver)
2xBC108 (or similar npn) only for switch-function
5x 220 Ohm
4x 10 KOhm
5x 1 µF/16V (micro Farad) tantal-capacitors
1x 100 µF/16V (micro Farad) electrolyt-capacitor
5 DIN-sockets for the MIDI-connections
1 SUB-D female plug 25 pin
short piece 9 wire-cable (shielded)
What kind of connectors at the PCB you are use, is your choice.
A small METAL case (100x70X30);
!!!It is very important for shielding radiation!!!