Wiring Question

M

Moley1390

Canberran Amatuer
Newbie question about wiring...

In an XLR balanced cable, I understand that the two core wires carry the signal (in opposite phase?) to cancel out interference induced in the cable (since both would be affected the same way, right?). SO! for the ground/shield part, what kind of electronics takes place here? I would particularly like to know why this must be independent for each cable, and why a common ground is not sufficient... or is it? I have no idea!
All of this was inspired by seeing a site - http://www.violetaudio.com/index.php?option=com_content&task=view&id=21&Itemid=30 - where they carry balanced signals over cat5 connectors, and charge a HEAP for it... And i wanted to know if that is deserved, or if i could just make them myself for a few bucks (i can solder, and have made leads in the past that work great)

THANKS for any explanations, you can probably see i have no idea :)
 
Violet make digital 'multicores'.

The signals from the stage go into a stage box, then into a A/D converter. From there they go through a twisted pair cable to a D/A converter, then into a mixing desk.

They don't carry balanced analog audio signals . . . they carry digital pulses.

While you could expect the cable to be significantly cheaper than a multicore, it's the bits at the front and back that make this an expensive method.

However, I expect the price will come down in time. It's a neat way of doing things.
 
Ah that would explain the price! Can you transmit balanced over cat5, if you wire up the right connectors? I know that's probably really bad for the signal, but hypothetically?
 
Moley1390 said:
Ah that would explain the price! Can you transmit balanced over cat5, if you wire up the right connectors? I know that's probably really bad for the signal, but hypothetically?
Click to expand...

Yes, you can; it will work fine electrically but won't be very durable in typical use. You can share ground between mics; a multichannel preamp will terminate all the pin 1s together anyway. Unless I am mistaken though, cat 5 doesn't have a shield. If you try to terminate it to four channels I would expect it would last about 15 minutes on stage, if that.

For installed it would be OK.

The digital snake thing can also be done with ADAT lightpipe.
 
I don't think it has a shield either... so would the max number of transmittable channels be 3, plus a common ground, for installed? This would leave one pin spare...
 
Moley1390 said:
I don't think it has a shield either... so would the max number of transmittable channels be 3, plus a common ground, for installed? This would leave one pin spare...
Click to expand...

Which you could use to double the ground. I still don't recommend this; balanced audio is usually OK without a shield but cost of having to redo installed cable vs. the cost of a proper audio cable makes it not worth trying.
 
It works!

I made one today, I won't rely on it in any way, but it certainly works! Cat 5 cable is just so much cheaper than mic cable! I know why, but it's still great.

Thanks to everyone for the help!
 
As a part time electricians i believe that the reason for a shield is that in certain cases with analog signals, cables must have a shield around them to get rid of electrical noise, that is some time generated by fluorescent light fitures, CRT monitors or being next to high voltage lines etc.

The shield helps take the unwanted noise to ground, atleast thats what i use it for in my field of work.

What zzed is saying is that the signal is converted to digital from stage then next to mixer it is conveted back to analog, so there is no reason for a shielded cable needed as digital signals are not effected by noise, only analog signal are.
 
But these particular analogue signals are balanced for that very reason, right? So the shield certainly helps, but for an installed balanced line is not ABSOLUTELY neccesary? I just mean that the signal wont get too degraded, will it? Sorry i'm asking so many questions, i don't want to state anything as fact, because i'm not actually sure!
 
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