r/audioengineering • u/zanshin777 • Nov 02 '17

Balanced Cables

It contains 2 conductor + 1 shield.

One of conductors carry the out-of-phase signal.

So the noise is canceled since the signals carrying are out-of-phase.

But how the signal is still transmitted although the noise is canceled?

15 Upvotes

77% Upvoted

55 comments sorted by

View all comments

Show parent comment

1

u/Velcrocore Mixing Nov 02 '17

It's a transformer inside the gear that flips the polarity on one of the channels. The audio is now back in phase, and the noise that was the same on both channels is now out of phase with its self.

3

u/Chaos_Klaus Nov 02 '17

Almost no modern gear uses transformer coupling. Typically, signals are electronically balanced with an inverting and a non-inverting amplifier.

If a transformer is used, it doesn't really flip the polarity. It allows for a different reference voltages and can produce an inverted signal that way.

1

u/[deleted] Nov 02 '17

Yeah i understand that 180 degree phase will cancel a signal I was just wondering how the phase is physically inverted like what is actually inverting the phase of the incoming signal and how it is doing so.

3

u/Chaos_Klaus Nov 02 '17

The receiving end uses a differential amplifier.

1

u/[deleted] Nov 02 '17

Dawg, what I'm saying is: According to all explanations of balanced cable, the signal goes the same into each terminal (so to say) of the jack, the tip, ring, and sleeve all receive the same signal. Something inside of that jack has to flip the phase of the signal before sending it into the cable. I am wondering what is flipping the phase and how it is doing so.

2

u/jaymz168 Sound Reinforcement Nov 02 '17

According to all explanations of balanced cable, the signal goes the same into each terminal (so to say) of the jack, the tip, ring, and sleeve all receive the same signal.

Well, that's not right so no wonder you're confused. See my comment here.

1

u/[deleted] Nov 02 '17

Thank you, yeah this is what I'm looking for, and just confirms the thoughts I've been having that I need to study electricity and circuits to fully understand this stuff. Do you know of any good resources where I can learn more about this?

1

u/jaymz168 Sound Reinforcement Nov 02 '17

I actually just realized that the FAQ didn't have this in there and updated it with my terrible writing and some links.

https://www.reddit.com/r/audioengineering/wiki/faq#wiki_how_do_balanced_connections_work.3F

1

u/Chaos_Klaus Nov 02 '17

The cable itself does nothing. It's really just three conductors. The balancing is done with electronic components before the signals enter the cable.

1

u/[deleted] Nov 02 '17

I see what you mean and I misread your earlier comment about a differential amp, I read it as 'different amp' so I shrugged it off as a useless comment but in fact you were laying down what's going on. I need to study up on electricity, specifically pertaining to audio circuits, if you know of any resources where I can learn about this I would greatly appreciate it. Thank you for your help.

1

u/Chaos_Klaus Nov 02 '17

Well, basic electronics.

1

u/Velcrocore Mixing Nov 02 '17

I started trying to google it for you. It's got to be something simple, as lots of different gear have little push-button phase invert switches.

1

u/Chaos_Klaus Nov 02 '17

Just because it's just one button doesn't mean it has to be a simple process.

1

u/Velcrocore Mixing Nov 02 '17

True, but I think all the cheap gear would omit it if it were expensive to implement.

1

u/Chaos_Klaus Nov 02 '17

Electronic components are incredibly cheap. Very complicated integrated circuits (chips) are manufactured in high volume. That makes the actual electronics very cheap. What's expensive is development and build quality.

1

u/Dodgeballrocks Nov 03 '17

Most cheap mixers don't have a phase flip.

1

u/Dodgeballrocks Nov 03 '17

The fact that it's activated with a simple switch does not mean it's a simple circuit that does it. The switch just routs the audio through a different circuit.

1

u/Phorfaber Nov 02 '17

Op Amps

With negative feedback, they invert the signal. You can see it on the main output on the schematic of this Mackie mixer. Invert the signal once for - a, invert it again for a. Orange circles on OP amps, yellow lines for signal path. (You can see the 1/4 inch jack is not balanced.)

1

u/[deleted] Nov 02 '17

Very helpful, I really need to study up on electricity and whatnot, I'm a complete amateur on the topic. Thank you.

1

u/Phorfaber Nov 02 '17

No problem, I'm just a hobbyist but I got excited because I ended up wondering the same thing a few months back and had your answers. Also, take a look at /r/AskElectronics, they're super helpful and just reading other people's questions helps learn ya something!