Convertin AF signal from unbalanced to balanced

[dipsi111]

Hello !

Anybody have some simple schematic for converting an unbalanced (RCA) audio signal (from PC sound card) to balanced and then back from balanced to unbalaced ? I need the schematic because I have to transport the audio signal from PC sound card to amplifier which is located 30m away from it. I'm searching for an simple solution because the quality of transmited audio is not so critical.

Another question is, can I use UTP (4 twisted pairs of wire inside) cable for the transport of balanced signal ? The UTP cable is not shilded ! I ask this because I have this cable installed already and if it is possible I would use it .

Thanx !

 

[flatulent]

The simplest way is to use audio transformers on each end. They are specified by the power level and impedance of the source and load the work into. Put 100 ohms in shunt with the destination end and use 100 ohm to 100 ohm transformers.

You can try the unshielded cable first to see how much extra noise it picks up. One way is to put a 10 ohm resistor across the sending end and 100 ohms across the destinatin end and an oscilloscope or audio amplifier across the destination end and measure the noise level. I suspect that it would be much less than the 100 mW or so output of your sound card.


There are active ways to do this but they are not any better than the transformer way and are more cumbersome to build.

 

[Zedman]

If balun like transformers are hard to get here,
what are the other ways to get balanced audio signal?
Or can I make transformers for this?

I also would like to build an audio over UTP project
and searching for the cheapest way.

Flatulent please can you post a small schematic about your
concept above?

thanks in advance,
Zed

 

[Zedman]

Will these schematics with OpAmps work?
Is it possible to build it with single supply opamps?

please help,
Zed