MUX

[ivconic]

8 channel example:

[ivconic]

int Ctrl_A = 7;
int Ctrl_B = 6; 
int Ctrl_C = 4; 
...
  pinMode(Ctrl_A, OUTPUT);
  pinMode(Ctrl_B, OUTPUT);
  pinMode(Ctrl_C, OUTPUT);
...


// ***** TRUTH TABLE *****
//  C    B    A     "ON" Channel(S)
// ***  ***  ***    ***************
//  0    0    0           0
//  0    0    1           1
//  0    1    0           2
//  0    1    1           3
//  1    0    0           4
//  1    0    1           5
//  1    1    0           6
//  1    1    1           7
// *********************************  


    digitalWrite(Ctrl_A, value); // HIGH or LOW
    digitalWrite(Ctrl_B, value); // HIGH or LOW
    digitalWrite(Ctrl_C, value); // HIGH or LOW

[ivconic]

or using direct pin manipulating (approx 12 x faster):

  DDRD |= (1<<DDD7) ; 
  DDRD |= (1<<DDD6) ; 
  DDRD |= (1<<DDD4) ; 
...


// ***** TRUTH TABLE *****
//  C    B    A     "ON" Channel(S)
// ***  ***  ***    ***************
//  0    0    0           0
//  0    0    1           1
//  0    1    0           2
//  0    1    1           3
//  1    0    0           4
//  1    0    1           5
//  1    1    0           6
//  1    1    1           7
// *********************************  




// PORTD &=~ (1<<PORTD7);  // (LOW); // OR
// PORTD |=(1<< PORTD7);   // (HIGH);
// PORTD &=~ (1<<PORTD6);  // (LOW); // OR
// PORTD |=(1<< PORTD6);   // (HIGH);
// PORTD &=~ (1<<PORTD4);  // (LOW); // OR
// PORTD |=(1<< PORTD4);   // (HIGH);

[ivconic]

This was specific demand, to select between 8 stereo channels.
Things can be more interesting if inhibit was included in to be controlled by mcu.
Davor pointed me on Vee "problematic" when line level signals are switched so i added 7660 as the easiest choice for me at the moment.
Things can be done even simpler.
...
Consider this as Easter treat.

[ivconic]

Two more pins to separately control inhibits = 16 single channels (pcb not valid in this case).