I have a backplane where 4 individual modules plug into it and provide various sound effects. To control which module is powered and to route the input signal to it, there is a 2-pole, 5-way mechanical switch so the power and signal are sent to the desired module. However, the output signal from each module shares the same trace going to the amplifier.
This is a problem because when more than 1 module is plugged, in the output signal goes south. Individual modules work great, but with more than one module installed, not so good. I thought that since the other 3 modules were not powered they would have no effect on the active module, well, I was wrong.
So I was trying to think of a way to route the input signal and power to the appropriate module and separate the output signals so they are not in parallel. That led me to see if I can use one of the poles of the switch for both power and input signal and the other pole for the output signal.
Two other thoughts were to add a diode to each of the output traces or an audio transformer. I just don't know, I already have hardware built so I am stuck trying to make what I have to work.
Do you think this will work or have any suggestions about the idea of adding the power to the input signal?
Best Answer
The cheapest solution would be to use a 3 pole 5 position switch and use the 3rd pole to switch the outputs. It is possible to combine the input and DC voltage into one line, but that brings up new complications. The input signal could be coupled to the DC with a capacitor, then extracted by using a second capacitor on the amp end. Problems to overcome with that would be power supply ripple would need to be very small, and you need to deal with impedance matching on both ends. A third solution could be to use individual relays at each amp module location. The switch would energize a 2 pole relay that which would switch the input & output.