phantom power and phase

[Light]

In an unbalanced cable, cold and ground are the same wire. Switch the leads, switch the polarity, by definition, I think. At any given instant, the voltage is swinging the opposite direction than an identical circuit wired with correct polarity.

Someone beat me if I'm wrong.

The ground in an unbalanced signal does not carry signal.

I think the problem here may be a misunderstanding of what a balanced signal is. I get the impression from an earlier post that you (or someone) thinks that in a balanced signal, the positive wire carries the positive electrical information, and the negative wire carries the negative information. This is NOT what happens.

In a balanced signal, the hot and neutral conductors carry the exact same signal, except the neutral signal is polarity reversed. The point of this is so that whatever RF interference is incurred over the transmission run (the length of the cable) is the same on both wires. Now, if you were to simply sum the two lines at the end, you would have really loud RF interference, and the signal would cancel out. However, that is (obviously) not what happens. When you get to the destination (usually the mixer), the neutral signal has its polarity inverted again, so it now lines up with the hot signal. The cool thing is, the RF interference which was pickup along the way also has its polarity reversed, which means you are summing the exact same RF interference, with polarity reversed. We all know what happens then, right? No more RF! Cool!

There is no way to invert an unbalanced signal, short of sending it through some form of balancing transformer. You may, depending on your mixer, be able to use its balanced inputs, however. A cable which sent the hot conductor of an unbalanced signal could be sent to the neutral of a balanced input (pin 3 on XLR, or the sleeve on a TRS). If it is a true balanced input (they are not always), then that would invert the polarity. It all depends on you gear. You could also invert it digitally, if you are recording in your computer.


Light

"Cowards can never be moral."
M.K. Gandhi

 

[Marik]

Here is another thread on the topic:

http://recforums.prosoundweb.com/index.php/m/0/1717/0/1759/?SQ=4d7e7d790f800ec581e0a6a3dc7612e3

 

[dr.colossus]

You may, depending on your mixer, be able to use its balanced inputs, however. A cable which sent the hot conductor of an unbalanced signal could be sent to the neutral of a balanced input (pin 3 on XLR, or the sleeve on a TRS). If it is a true balanced input (they are not always), then that would invert the polarity.

so all in all your mixer takes what ever is on pin 3, inverts it and "adds" it to pin 2... i see how this could work, but do you mean ring of a trs? and leave the tip/pin two with no signal at all?....

i've seen circuit diags for tube phase splitters, which takes a signal and creates an inverted signal aswell as an equally amplified (effected) copy of the uninverted signal.... its seem the only way to flip a d.c. is through some sort of active device. a small transistor class "a" 0 (unity?) gain amp would do the trick to but i would surely be adding noise...

i will try lights suggestion... thanks for the link marik i will read it after work (its friday! its friday! woohoohoo)

 

[Light]

its seem the only way to flip a d.c. is through some sort of active device. a small transistor class "a" 0 (unity?) gain amp would do the trick to but i would surely be adding noise...

Precisely, which is what I am suggesting. Use the transformer (or how ever they are doing it) in you mixers balanced inputs to do the job, instead of buying a seperate box (which will probably be expensive, because transformers are almost always expensive).


Light

"Cowards can never be moral."
M.K. Gandhi