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balance vs unbalanced

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Posted on April 26, 2015 at 17:43:38
rockanroller
Audiophile

Posts: 84
Location: ohio
Joined: March 29, 2015
 Hello. Would someone be so kind as to explain balanced versus unbalanced connections? and all related info.
That would be really cool!
Just trying to learn. thanks.

 

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RE: balance vs unbalanced, posted on April 26, 2015 at 18:00:00
Metralla
Audiophile

Posts: 7801
Location: San Jose, California
Joined: January 30, 2001
 look for Ralph's posts on the topic.


Regards,
Geoff

 

RE: balance vs unbalanced, posted on April 26, 2015 at 18:18:39
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 An unbalanced interconnect has two wires, one carries the audio signal and the other is ground. A balanced interconnect has three wires, two of which carry the audio signal and one is ground. The two that carry the audio signal are 180-degrees out of phase with each other and the audio signal is extracted using a differential amplifier that detects out-of-phase signals only and rejects in-phase signals. The theory behind a balanced connection is that any noise picked up by the interconnect will be in-phase and thereby rejected at the amplifier input. In other words, only the audio signal will be transferred from one component to another without any additional noise. This allows very long cable runs with balanced interconnects without picking up any unwanted noise along the way. Professional equipment always use balanced connections because they often require long interconnects that sometimes exceed 100-feet.

Best regards,
John Elison

 

RE: balance vs unbalanced, posted on April 26, 2015 at 23:39:52
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 A lot of people will confused balanced and unbalanced cabling interfaces with circuit topology, especially differential input/output stages. Manufacturers have even gone as far as to invent a new term: "Truly Balanced", which carries a murky technical definition and seems to be more targeted towards the marketing side of things.

I suggest reading the entire whitepaper I have linked to. In specific, pay attention to those notes in italicized printing.

 

RE: balance vs unbalanced, posted on April 27, 2015 at 01:49:21
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 I think the following paragraph from the white paper you referenced says pretty much what I said on the subject. A balanced connection must include a differential input at some point otherwise it cannot reject the noise picked up on the interconnect.



 

RE: balance vs unbalanced, posted on April 27, 2015 at 06:03:42
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004



It's funny that you can read that paper and come to the conclusion that a balanced connection must include a differential amplifier. The paper actually says the complete opposite.

 

Its helpful to know some history!, posted on April 27, 2015 at 11:02:51
Ralph
Manufacturer

Posts: 4769
Location: Minnesota
Joined: April 24, 2002
 The balanced line system arose out of a need for long distance telephone communications. Essentially, it made transcontinental phone calls possible.

Seeing the obvious advantages the recording and broadcast industries picked up on the technology after WW2. Suddenly you didn't have to have the microphones and the recorder in the same room as the musicians!

During the 1950s the industry needed connections from the new emerging hifi market. RCA had an inexpensive connector they were using to send signals from their television tuners to the intermediate frequency amplifiers in their TVs. This got adapted by the audio industry and is still known as the RCA connector.

Unlike the balanced system there is no termination standard for RCAs. With a balanced setup at the time that usually meant a transformer (and still does today); such a part was seen as expensive and the cables were not expected to go a long ways so no termination standard was ever developed for RCA connections. In addition of course the return connection for the RCA connector has to travel on the ground connection.

The result of these two aspects is that the quality of the cable can make a big difference with what you hear when running single-ended connections. By comparison, if set up correctly (meaning that the associated equipment supports the balanced standard) you will not hear any differences between balanced cables regardless of cost; it is as if the interconnect cable does not exist so far as its contribution to the overall system is concerned. IOW they are absolutely neutral.

Many people object to this latter comment, drawing on personal experience. It is not that their experience is not valid- in such cases it is because the equipment used does not support the balanced standard.

 

RE: balance vs unbalanced, posted on April 27, 2015 at 11:09:53
John Elison
Audiophile

Posts: 23900
Location: Central Kentucky
Joined: December 20, 2000
Contributor
  Since: January 29, 2004
 > It's funny that you can read that paper and come to the conclusion that a balanced connection must include a differential amplifier.

What you've shown is a passive balanced output. This still requires a differential input to be meaningful. In other words, the only way to to reject noise is to have a differential input. Consequently, the only advantage of the passive balanced output shown below is if you have a differential input on your amplifier. Of course, I'd imagine the differential input could be accomplished using a transformer in place of an active differential amplifier.

I hope you realize there are two parts to a balanced connection that include the balanced output of one component to the balanced input of another component. You don't have a balanced connection without both. I also hope you realize that a passive balanced output contains an audio signal on only one of its two signal lines. The other line contains only noise picked up by the interconnect. Therefore, without a differential input at the other end, there is no way to reject the noise.

Anyway, I guess the original poster can do his own research and make up his own mind. However, when I explain the important points of a balanced connection to someone who obviously knows nothing, it's the differential input receiving two balanced out-of-phase audio signals that describe the essence of a balanced connection.

Best regards,
John Elison

 

RE: balance vs unbalanced, posted on April 27, 2015 at 13:29:51
Caucasian Blackplate
Industry Professional

Posts: 8313
Location: Seattle
Joined: June 18, 2004
 "What you've shown is a passive balanced output. This still requires a differential input to be meaningful."


You are absolutely 100% incorrect. Transformers reject noise on their own. Also, what if we have a push-pull input stage on the amplifier? You're missing the point: Balanced/unbalanced connections can function independently from the circuitry that follows them.

"In other words, the only way to to reject noise is to have a differential input."

No, you can use a transformer.

"Of course, I'd imagine the differential input could be accomplished using a transformer in place of an active differential amplifier."

This is sort of like saying that you could make a cup of coffee with the pacific ocean. The transformer doesn't make a differential input, it makes an isolated balanced input.

 

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