Hi. I want to make a crossover 4x4 switch for audio signals. A switch where one mono input can be connected to one mono output at a given moment in time. I am thinking of using several 74HC4067 multiplexers under the control of ESP32 for this task.
Each output (amplifier) will be assigned it's own multiplexer. ESP32 will control these multiplexers to connect needed input to needed output. For example:
1 input -> 2 output
2 input -> 4 output
3 input -> 1 output
4 input -> 3 output
I have a few questions so far:
- Did I choose the right circuit and components for my task?
- How do I connect grounds in such a circuit?
- How to synchronize the actions of multiplexers correctly? Could something bad happen if several multiplexers select one source at the same time?
I don't want this circuit to make noise also.
My knowledge in electronics is very limited, but building this doesn't look too complicated. I will probably increase number of inputs and outputs in the final version, but for simplicity I made a 4x4 scheme.
The 74HC4067 will switch analog levels between Gnd and VCC. If you are switching line level voltages, typically 0 +/- 1V up to +/- 2.5V, then you should consider buffering the incoming signals to get them up 2.5V +/- 1 to 2.5V, then move them back to 0 +/- 1 to 2.5V on the output side.
One way to do that is to use series capacitors and resistors.
The other thing to consider is that each 74HC4067 will act as a series resistor when turned on. Driving AC into two or more series resistors may impact the AC signal vs just driving one series resistor. Active buffering of the source signals before feeding them into the 74HC4067 would be a solution.
I once made a sort of mixing board for practice with my band. 8 mics or instruments could plug in, each input was buffered via op amp, and fed into a summing op amp that then was buffered to drive up to 8 headphone driver outputs. Each output had it's own set of pots so every listener could set the mix levels they wanted to hear, typically more of themselves and less of others.
All the signals were kept centered around 0 so no capacitors were needed to remove DC levels.
Took a while to wire up 64 pots and the 8 inputs & 8 outputs, but it worked well for us.
Surely 74hc4052 would make more sense? Unless you plan expand to many more input channels later.
I would second a 4051 or 4052 powered from +/-5V and Gnd as a better choice.
ESP32 seems overkill for controlling switching, unless it is being used for its wireless capability.
Yes, muxer with a -VEE pin, like the 74HC4051, make more sense for ground-referred audio signals.
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