microphone over ethernet-cable

[stefan75]

Hi,
in our building every room has a cat5 cabeling.

Is it possible to put a smallmicrophone to a RJ45 line and on the other sinde of the cable a 3,5 connector to the soundcard of a pc ?

Could this be functional ?
Or ist the wire to thin ?

Thanks in advance.
Stefan

[sammyhe]

hi

i would love an answer as well. i've already tried breaking up a basic microphone but it seems they're very sensitive to unshielded cabling and stuff.

i couldn't get it working across the ethernet.

any other ideas? i'm loathe to spend $300 on an ethernet camera with audio when there is a cheaper and more elegant solution.

also i'm concerned the ethernet camera will need power.

thanks

[mjj9994]

Tough situation there... unfortunately.. i believe the VOIP / video over IP has to convert the signal to digital format to utilize the cat/ethernet cable. The only solution I know of would be to get a type of converter (ie.. webcam server, etc) and connect the microphone through it.

Also, you may want to set up a router so the new occupant does not ask why their ethernet connection is not available or being used.. and may also need the ethernet IP address of the target room to configure the server. As for the power... I think they do require separate power (plus you may also need separate power for the mic as well).

I havent delved into these gadgets too much.. this info is mainly just from browsing the equipment specs on catalogs.. so I may be way off, but that is the jest of what ive read

- Mark

[sammyhe]

okay i got a working solution here. i basically got two female RCA plugs and wired two strands of UTP wire to each plug. this allows for stereo. then i got a stereo mini jack to male RCAs and plugged the mic into that.

the on the PC side i used another two female RCAs and got an male RCA to male mini jack which plugs into microphone in on PC.

voila. there is some minor interference and loss, but it seems to work okayish. the UTP (and mic) are on the shelf of the cupboard.

and that is it. no results yet. will post as soon as there are.

[reggind]

UTP wiring is really not ideal for low level audio signals. That being said there are a few things that you can do to improve the situation.

One of the simplest things you can do is amplify the signal from the mic and run the amplified signal over the UTP cable. Radio Shack used to sell a little amplifier just perfect for this. This does two things for you. First it provides a low impedance output that makes it much harder for extraneous electrical noises to interfere with. Second, it gives your signal a boost, so you have a higher level signal going over the wire. You might be able to run power to the little amp over another pair of wires in the UTP cable. The amp I am thinking of ran off a single 9V battery.

If the amplifier and power is too much, you may be able to find a pair of small audio output transformers from old transistor radios. These typically went from the output transistor to the speaker. On the mic end, you need to run that into the winding on the transformer that went to the radio side and the UTP gets the side that used to go to the speaker. Note that if it is a condenser mic that you will need to power it, or run power to it over another wire in the cable. On the other end you would connect the speaker side of another transformer to the UTP pair and the radio end to your input jack to your recorder. This set up lowers the output impedance of the mic greatly. This helps keep electrical noise out of the audio. It also greatly lowers the level of the audio going through the wire. The transformer on the other side increases the signal level and increases the impedance.

If you can get good transformers you can balance the signal and lower the impedance. This is how professional mics are wires (balanced, low impedance) but they use much higher quality cable. You could even provide phantom power for preamps in the jacks at the far end.

In general just running a mic through a length of UTP is going to give you a lot of hum and noise unless you do something.