100 microphones on long cables, how?

[Zedman]

Hi,

I would like to implement a voting system with switchable mics on
every voting client. Only one can speak at one time. And I want
to record it with a PC.
I think the MCU in the client will switch the mic on with an optocoupler,
if the software in the PC allows it.
The clients will be on a RS485 serial network, and i would like the mic's
signal to be on one other line in the UTP cable beside the RS485 lines.

But what kind of amplification do I need on the mics?
Or I need special shielded cable and no amp, or I have to amplify
each client's signal to a higher voltage and it can go on the UTP? :roll:

please teach me,
thanks
Zed

 

[divan]

why don't use something like OPA+atTiny26 on client side with rs485 protocol software and analog signal digitizer / packet transmitter . this case you can use utp to host for control and speach transmission .

 

[Zedman]

I don't have time (project deadline is to close)
to implement A/D conversion and digital
transmission. So i decided to go with analog voice
and the PC's mic-in.

Is it possible?

 

[bimbla]

Yes, very much possible!

Implement 10 X 10 input adders and add the o/p of the 10 adders to get one signal. Locate this circuit as close as possible to the stage. Keep suitable gain. Carry this to the place where you are keeping the amp and other stuff. Condition the signal for reqd. freq response and give it to the power amp. It should do. You can have a single bass, treble and volume controlling all the mikes. This will save you time and get the job done.

DO NOT COMPROMISE ON THE WUALITY OF MIKE CABLEES USED.

If you wan more details, specify.

bimbla.

 

[Zedman]

thanks bimbla,

Actually I need only 60 clients, but I can add an
OP amp to every client. Is it ok to add them (60 pieces)
parallely to a good mic cable, and feed it to the PC's
line in?
I can't really make matricies, because they can
move the clients for ex.: 6x10 or 8x8 etc.
Does it need separate GND line? Can I connect it to
the digital GND?
How large amplification do I need? (1-1.5Vpp?)
(I also need a small mic preamp schematic,
I am not really good in analog tech)

thank you very much
for the help,
Zed

 

[bimbla]

Please do not connect the Mike cables in parallel.