Re: Computer control of an audio multiplexor

[Lewis Gardner <lgardner@xxxxxxxxxxxxxxxxxxxxxxxxxx>]

Joe User wrote:
> I am trying to multiplex a number of radios into the 'Line In' on my
> computer sound card.

I assume you really want to select one of the radio outputs to go to the
sound card. Multiplexing is a different technology
en.wikipedia.org/wiki/Multiplexing


> I want to send commands from the PC, through the RS232 serial port, or
> the USB.
>
> I want the radio signals to be switched according to the commands from my
> PC.
>
> I need the switching to be 6 stereo signals to 1 stereo signal.
>
> Has anyone done this?  What is the cheapest, easiest and most flexible
> way to do this?

It all depends on how you define cheap and easy.

If you are handy with a soldering iron and writing simple programs then
using the parallel port to control 6 DPST relays would do what you need.
With a well supplied junk box you could do it for under $20.

Here are some links:
www.epanorama.net/circuits/parallel_output.html
ourworld.compuserve.com/homepages/Bill_Bowden/page6.htm
www.dakeng.com/relay.htm
www.electronickits.com/kit/complete/elec/ck1601.htm


Even though I could easily do the above I would opt for the eBay route.
What you are looking for is an audio matrix switch with RS232 control.
Since you have 6 inputs and only one output then anything larger than a
6x1 switch.

Here are links to VERY NICE AutoPatch half-y units:

cgi.ebay.com/autopatch-half-y-matrix-composite-switcher-with-audio_W0QQitemZ180187334290
cgi.ebay.com/AutoPatch-Half-Y-8x4-Stereo-Audio-Video-Matrix-Switcher_W0QQitemZ320188063634

For my money I would use one of these to do the job. I have done several
AutoPatch installations and their equipment is top quality. While you
don't need 1/2 of what these units will do the price is right! Notice
that the terminals on the first listing are removable screw type while
the second listing has RCA terminals which might be handier.

Control software and protocol can be found:
autopatch.com/index.php?object=286
autopatch.com/pdfs/bcs/bcs_serial_control_protocol.pdf

Marc Hult (who posts here regularly) has some Ivie 784PW 8x4 audio
matrix mixers in his porch sale for $70. Here is a link:
www.econtrol.org/porch_sale.htm


If you like buying new then these are some audio only switches that
could do the job:
www.rdlnet.com/product.php?page=157
www.kramerelectronics.com/indexes/item.asp?desc=324


Other options include using RS232 controlled relay cards like these:
www.6bit.com/products/smartrelayS.php?products_id=34
www.pencomdesign.com/pencomstore/agora.cgi?p_id=0037


> I've never used X10 stuff, and would like to avoid it, if I could easily
> do this with a simple USB device.

Since all the controlled relays are local X-10 is not an appropriate
technology. When used properly X-10 can be quite reliable.

Good luck with your project. If you need more information please reply
with a bit better description of what types of radios, type of computer
and a better description of the total project.