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I am new in electronics and I'm working on a personal project with Raspberry Pi that I need help. I want to make a board that allows to commute 4 audio inputs (TV, MP3, DVD, FM web) in 4 audio outputs (speakers), can be simultaneously. Whereas that 1 audio input can be routed to even all outputs. All managed by the Raspberry Pi. From what I researched, I have to use microcontrollers and do the DAC to the speakers. Is it? Searching about microcontrollers and ICs I found the PIC18F4550 microcontroller and 74HC4067 Multiplexer/Demultiplexer. Sounds good to solve my problem. Can I do the routing between inputs and outputs with one of them or both together? Is possible to control this with RPi? Some expert could help me and show me any example or circuit, please?

Sorry, but I don't know almost nothing about electronics and components... and my english is bad.

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closed as too broad by placeholder, Daniel Grillo, JYelton, Rev1.0, Chetan Bhargava Aug 21 '14 at 3:44

There are either too many possible answers, or good answers would be too long for this format. Please add details to narrow the answer set or to isolate an issue that can be answered in a few paragraphs.If this question can be reworded to fit the rules in the help center, please edit the question.

2 Answers 2

up vote 2 down vote

You need a switch matrix made of relays or analog muxes to connect a specific source to a specific (or many) targets. A simple MCU can do that.

If you have to do ADC conversion of each input, RPi can be more of a help. Possibly you need external ADC with proper sample rate and bit depth and multiple channels. You also need multiple DACs.

But, I do not see sound to digital and then back to sound conversion if there is no need for digital processing.

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Thank you, NVD. I'll search about MCU. –  Marco Antonio Aug 20 '14 at 20:10
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By 4 audio inputs you presumably mean 8 channels (4x stereo inputs) and 4 stereo outputs. The simplest way to achieve this is a matrix of 16 relays, each of which is 2-pole (one pole for the left channel, one pole for the right channel) in a crossbar arrangement.

However, this glosses over the issue of mixing multiple inputs into one output, which may or may not be critical to your application; with input & output buffering it is not a problem to cross-connect with relays like this, but when you join two inputs together to one output, any other output connected to one of those inputs will get the "mixed" signal (of both inputs) too. Your description does not make clear if this is acceptable.

If it's not acceptable you may need to use analogue switch IC's or some sort of switchable gain op-amp circuit, with 4x inputs to each speaker output that can be enabled or disabled without affecting the source signal.

However, this is not a new problem in the world or electronics, so some googling should turn up plenty of mixer / switch matrix / audio switch schematics.

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Thank you, John U. Sorry for not say that... but the output mixing is not acceptable. Can you show me an IC for this case? –  Marco Antonio Aug 20 '14 at 20:18
    
No, I have never had to do this so haven't researched IC's, but as I said in my answer it's by no means a new or unusual problem in the electronics world. Google is your friend. –  John U Aug 21 '14 at 8:58
    
Ok, John. Thank you very much. I'm already on Google... –  Marco Antonio Aug 21 '14 at 18:26

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