I've built something similar, it takes in 10 stereo audio signals and it can
distribute it through 8 different outputs. It's controlled of a pic16c73 via an
RS485 network. I've built this for home and am buiding a similar matrix switcher
for video, slowly building up my home automation system.
Regards
Stuart

John Perkinton wrote:

> I design public adress systems, and multizone music systems for a company in
> dundee in scotland, which are installed in a large number of sports clubs
> thoughout the uk. My current system gives sixteem channels of different
> music which is selectable from a wall mounted face plate with lcd display to
> let you know what channel you are listening to. The system is card based, so
> can be expanded easily for both inputs and outputs, with an input card
> having 4 inputs which can take anything from mic level up to speaker level
> inputs, and the ouput cards having line-outs, and headphone jecks on the
> wall mounted face plates. The unit thansmits its audio over cat5 cable along
> with power. Each output has a selectable paging zone out of 24, and you can
> have up to 20 outputs on each zone. There is a 24 zone paging console, also
> connected via cat 5, with push button zone selection, and each output port
> has both 12V and 24V restoration if required. Volume is automatically
> increased when a zone is paged. When changing the channel you've selected
> the volume is ramped down then up to avoid nasty switching between channels.
> The main unit is housed in a 4U rack mounting case which contains the
> motherboard, containing the mic input, a firemans mic input for evacuation
> purposes, and a voice recording chip for fire purposes. This also has all
> the paging logic and has 14 card slots for input and output cards.
> The whole unit runs off of pic16c84 4Mhz chips. One for each output. One for
> the mic console. One for the motherboard. One for each channel/volume
> selector, and is powered from a standard PC power supply. I also have a
> fully encased version of the channel/volume selector so that they can be
> mounted on sports equipment, so people can listen to television
> cahnnels/music/radio whilst excersising, with several TV's on walls so they
> can listen to which ever channel they want, but in most rooms the outputs
> are taken to 100V line amplifiers and are distributed through ceiling
> speakers.
>
> For some reason, even though the audio quality is unsurpassable through the
> existing system, my boss wants me to design a digital audio version. This is
> going to be a nightmare, he wants 32 stereo channels, down one pair of
> cables. Everyone says its impossible including a few of my friends who work
> for Philips, but cable TV does it using Nicam so why can't I.
>
> Any ideas, or should I just look for another job, as I only get paid £17,000
> a year, and end up working about 75 hours a week with little or no holidays,
> no paid overtime. If you have any ideas please don't hesitate to contact me.
>
> Please also let me know of any projects you have done, and I'll let you know
> some other mad things I've done with PIC's.
>
> John Perkinton.