Audio Distribution System – Phase 1 – The prototype

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This project is intended to investigate the possibility of, and hopefully build if successful, a home-made externally-controllable matrix switcher with 8 inputs and 4 outputs using parts that cost a total of < £100 (excluding the external equipment such as amplifiers, speakers and cabling). The quality of the audio must be acceptable, but I'm not expecting it to be perfect - that's why the expensive matrix switchers exist. It just needs to serve the purposes of a small house.

There are many products on the market today to distribute audio around the house. They appear to fall into two categories: MP3 (and similar) wireless streamers targeted at consumers, and hard-wired matrix switchers aimed at professional installers. The former, while relatively cheap at £35-£250 per zone, is limited to playing pre-recorded audio encoded into one of it’s supported formats. These files must then (in most cases) be hosted on a suitable machine that they can be streamed from. The matrix switchers are significantly more expensive, and generally not available directly to consumers. These distribute actual audio signals from a number of inputs to a number of outputs, such that any one output can be connected to any one of the inputs, and outputs can share the same input connection.

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Initially the switcher will be connected via a parallel port to a host computer, which will run a dumb network server to relay commands from controllers around the house. The controllers will run some custom-written software (most probably as a web application).Inputs will most probably consist of some of the TVs around the house, plus the DAB radio in the kitchen and a computer to play MP3 and other audio files.

The prototype has been built, and it will soon be plugged into an ATX power supply and brought to life – hopefuly without any accompanying burning smells! The ICs aren’t cheap nor easily obtainable, so if it goes wrong it’ll be a bit of a setback. The prototype mainly exists to test that the audio signal does not degrade significantly as more outputs are added to one input, and that the multiplexer ICs can reliably reproduce a line-level signal.

More details will be posted as this project progresses. Here are some photos of the prototype and amplifier to tide you over.

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