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.
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.