connecting PC to TV

unbalanced

Obviously the proof that you're wrong is that thing you pick up and talk on every day, the telephone. It doesn't need mu metal shielding, and the losses are not huge. THe bandwidth of telephone is limited because the signals have to travel for miles over twisted pair. For a simple in-house audio system with a few hundred feet of cable, the bandwidth can be much wider than the audio system. This is how the audio pros do it, over a 600 ohm balanced line.

Reply to
Watson A.Name - "Watt Sun, th
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Back in the days before amplifiers, the furthest you could call, was from about New York to Denver, so you don't need an amplifier to talk across town. Also, it's entirely possible to pass DC power through a balun, though it require appropriate split winding transformers and blocking capacitors.

Reply to
James Knott

transport

That's _was_ an important difference. The telephone system wouldn't go far without power, back a hundred years ago when there were no amplifying devices, such as transistors or tubes. Nowadays, with self-powered telephones (cordless, or any phone that runs off a wall wart), or modems, faxes, etc, there is no need for power, other than for signaling the condition of the line. So, wrong again.

That wasn't true a hundred years ago, and is becoming increasingly unlikely nowadays, where the signal comes into the equipment and is digitized by a codec. Again remember that most of the phone system was designed a hundred years ago when there were no amplifiers, no tubes or transistors.

Generally, audio amplifiers have inputs that are in the kilohms, but their outputs are usually much, much lower, in the hundreds of ohms. They are usually capable of driving baluns that are, say, 600 ohms.

For line levels you don't need shielding, but for mic levels, it best to have the shielding to protect against that RFI and ENI that might leak into the signal.

Reply to
Watson A.Name - "Watt Sun, th

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But there is an important difference :-) Two actually. Your telephone system won't go far without power. And most --if not all-- telephone lines apply amplification. Both go missing in the passive balun system we were talking about :-)

It is true that my assumption was wrong. But not for this reason. I was expecting a balun to transform the kilo-ohms audio signal into 110 ohms and back. Which, I still believe, would yield the results I feared. In practice, it is much simpler though. You don't need to match the cable characteristics, at least not for audio.

Well, I know, I am learning every day :-)

But I have yet to meet a professional audio installation that uses unshielded cable for it's 600 ohms balanced lines. (Although in the mean time I learned that even simply replacing coax with cat5 performs remarkably well.)

Reply to
Gerard Bok

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