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Justin89T
12-03-2004, 10:15 AM
Can someone give me an indepth explination of balanced vs. non balanced RCA outputs? I see it on an eclipse deck... the one without the internal amp (can't think of the model)

IIRC it was 8V balanced and 16V unbalanced... or somthing

anyway, i'd like to learn what it all means

_ Justin

maylar
12-03-2004, 01:48 PM
Balanced signal lines have been used by the phone companies for over 100 years. Picture a source with a transformer at one end... two wires to another transformer... then the receiver. The signal travels between the two wires, with no ground needed. Both wires have infinite impedance to ground. The definition of "balanced" lines is that both wires have the same impedance to ground.

The reason balanced lines are used is that they are immune to induced and radiated noise. Any ground referenced noise that enters the cable will be identical on both wires because of the equal impedances. The circuits at the receiving end (amplifier) are designed to amplify only the difference between the 2 wires and reject any signal (noise) that's common to both of them.

RCA cables are unbalanced... one of the signal wires is ground. Radiated and induced electrical noise is also ground referenced. Any noise that gets past the ground (RCA shield) becomes part of the signal and will be amplified at the other end.

`pr0digy
12-03-2004, 02:22 PM
To perhaps simplify a bit, balanced lines use two wires, and the phase is switched on one wire, and normal on the other. Any line noise induced is the same phase on both wires... At the end of the wire, a device switches the out of phase line, so now the intended signals go back together, but the noise is now out of phase, and cancels out.

Perhaps that was clear, I'm sure you could google for a better explanation.

maylar
12-06-2004, 01:17 PM
Balanced lines have absolutely nothing to do with phase. Nothing. It's all about impedances.

vactor
12-10-2004, 09:35 PM
Balanced lines have absolutely nothing to do with phase. Nothing. It's all about impedances.
a blalanced line does have to do with pahse, at least with regards to audio balanced lines. in a balanced line configuration, u have 3 signals. a ground, a positive, and an inverted. the ground is the reference. the signals are recombined (the inverted signal is re inverted at the end) and eny noise contained in both the positive and inverted lines will then have one of them inverted, and thus cancelled in the recombination of the 2 signals.

johnecon2001
12-12-2004, 11:25 AM
^ yup... as a pro audio engineer, thats pretty much right.. in laymens terms.

johnecon2001
12-12-2004, 11:25 AM
and its the 8053 that has no amp.

maylar
12-15-2004, 05:03 PM
^ yup... as a pro audio engineer, thats pretty much right.. in laymens terms.

Unfortunately, this is a common misconception even among professionals who should know better. It's not your fault.. there's dozens of web sites that define it this way.

a blalanced line does have to do with pahse, at least with regards to audio balanced lines. in a balanced line configuration, u have 3 signals. a ground, a positive, and an inverted. the ground is the reference. the signals are recombined (the inverted signal is re inverted at the end) and eny noise contained in both the positive and inverted lines will then have one of them inverted, and thus cancelled in the recombination of the 2 signals.

Sorry, that's wrong. ALL electrical circuits have 2 sides.. positive/negative, high/low, source/return, call it what you want. A single ended (non balanced) line just has one of the two wires at ground potential. In a balanced line, both wires are isolated from ground and have the SAME IMPEDANCE to ground. That's what makes it "balanced".

The IEEE Handbook defines a balanced system as one in which all legs of the circuit have the same impedance to some common reference point, usually ground.

It's not about phase. If you take a resistor and connect it from one of the 2 wires to ground, the impedances are different and the system is no longer balanced. The phase doesn't change. But the noise picked up by both wires will be different, and won't be cancelled at the receiving end. That's how a balanced line works.. balanced impedances.

d cha p
12-16-2004, 06:27 AM
So would this alleviate the need for me to run my power wire and rca’s on opposite sides of my truck?

squeak9798
12-16-2004, 09:49 AM
So would this alleviate the need for me to run my power wire and rca’s on opposite sides of my truck?

Um, that was never a concern before anyways. That whole "run the power wire opposite the RCA's" is a great big car audio myth. Run them down the same side, zip tie them together, whatever....it won't induce audible noise. I had two sets of RCA's (one for subs, one of comps), the remote-on (REM) wire, power wire, and two sets of speaker wire all zip tied together for the entire length of my full-size 4-door sedan, and guess what...........not a single issue with it.

squeak9798
12-16-2004, 09:55 AM
Unfortunately, this is a common misconception even among professionals who should know better. It's not your fault.. there's dozens of web sites that define it this way.

Sorry, that's wrong. ALL electrical circuits have 2 sides.. positive/negative, high/low, source/return, call it what you want. A single ended (non balanced) line just has one of the two wires at ground potential. In a balanced line, both wires are isolated from ground and have the SAME IMPEDANCE to ground. That's what makes it "balanced".

The IEEE Handbook defines a balanced system as one in which all legs of the circuit have the same impedance to some common reference point, usually ground.

It's not about phase. If you take a resistor and connect it from one of the 2 wires to ground, the impedances are different and the system is no longer balanced. The phase doesn't change. But the noise picked up by both wires will be different, and won't be cancelled at the receiving end. That's how a balanced line works.. balanced impedances.

Not saying I don't believe you (hey, I'm not an EE, I really have no grounds upon which to argue), but I have ALWAYS heard/read the same as the other guys; one signal is inverted, one not inverted, etc etc. I understood that the ground and relative impedences were part of the "system", but along with the inverted signal :confused:

maylar
12-16-2004, 02:07 PM
Not saying I don't believe you (hey, I'm not an EE, I really have no grounds upon which to argue), but I have ALWAYS heard/read the same as the other guys; one signal is inverted, one not inverted, etc etc....

People confuse the IMPLEMENTATION of a balanced system with it's DEFINITION. That's where the problem lies.

There are 3 ways to make a balanced line driver:

1) With a transformer.

2) With a dedicated line driver chip.

3) Or by combining 2 nonbalanced drivers (like RCA outputs) into one circuit. For this to work, one of the RCA's has to be inverted so that it is out of phase with the other. That's where the "phase" connection is. But that's not what defines "balanced", and that's not what makes the system immune to noise pickup. It's the equal impedances to ground that does that.

This scheme is unique to car audio BTW. Balanced lines are not.

jujumantb
12-16-2004, 03:08 PM
Um, that was never a concern before anyways. That whole "run the power wire opposite the RCA's" is a great big car audio myth. Run them down the same side, zip tie them together, whatever....it won't induce audible noise. I had two sets of RCA's (one for subs, one of comps), the remote-on (REM) wire, power wire, and two sets of speaker wire all zip tied together for the entire length of my full-size 4-door sedan, and guess what...........not a single issue with it.
I understand that it is not *supposed* to be a problem, science tells us they cannot interfere with eachother, but!, regardless of that, I have lots of first hand experience where, when run together, I get noise, seperate them, and I get none, coincidence? Perhaps, but it works.

squeak9798
12-16-2004, 07:36 PM
I understand that it is not *supposed* to be a problem, science tells us they cannot interfere with eachother, but!, regardless of that, I have lots of first hand experience where, when run together, I get noise, seperate them, and I get none, coincidence? Perhaps, but it works.

Moving a wire changes more variables than I care to count....you can't attribute the change to that single variable (moving the wire). If it were to induce audible noise, then it would do it everytime. And obviously it doesn't.

Not that I like RC all that much, and I'm not on his "bandwagon".....but RC will give you \$1000 if you can make an undamaged RCA and power wire being ran next to each other induce audible noise.

squeak9798
12-16-2004, 07:41 PM
3) Or by combining 2 nonbalanced drivers (like RCA outputs) into one circuit. For this to work, one of the RCA's has to be inverted so that it is out of phase with the other. That's where the "phase" connection is. But that's not what defines "balanced", and that's not what makes the system immune to noise pickup. It's the equal impedances to ground that does that.

This scheme is unique to car audio BTW. Balanced lines are not.

Ah....thank you :)

vactor
12-17-2004, 12:40 AM
pro audio gear uses 3 wire conductors all the time with one signal being inverted. it was my understanding that this was referred to in audio circles as being a form of balnced line transmission. yes, one can also do the floating ground via isolation transformer as well, but as far as cmrr i thought 3 wire inverted phase was best ... and u can do it via rca pairs, 3 wire connector and more ....