Source selector
This module has 4 inputs stereo RCA ports. It is accompanied by a mechanical rotary switch to allow input source selection.
This switch is already mounted on a separate PCB. The PCB also includes 4 slots already arranged to receive LEDs (supplied) thus providing a visual indicator of the active source.
To preserve the sound, no audio signal flows into the source selector. The rotary selector merely supplies pairs of S9014 transistors with HK19F relay to enable / disable each output port.
Each relay is associated with 1N4148 switching diode with low leakage current.