Today, on a different thread was asked what is the difference between a balanced and fully balance signal. Since there seems to be a lot of confusion and speculation I decided to create this thread to explore what a fully balanced signal is.
In a nutshell, fully balance is a fully balanced signal path from start to finish. That is an entirely differential balanced signal path from input to output; the audio signal never unbalances. It is done by providing identical internal signal paths for both the "non-inverting" and "inverting" audio signals. It is said to yield 3 dB better dynamic range.

 

Last edited: Mar 21, 2019

Thank you.

 

So it's just like dual mono topology?

 

They are 2 different things. You can have a balance dual mono amplifier or a fully balanced one. Dual mono is treating 2 channels totally independent from one another.

 

@Andrew here is an excellent article, albeit a little too technical for some people, about fully balanced amplifiers.https://hometheaterhifi.com/technic...r-amplifier-advantages-and-design-challenges/

 

I would be a bit skeptical about using balanced or fully balanced for other use than signal transmission. There's a lot of snake oil surrounding the 'balanced headphones' concept. Larger transducers are not very different in that aspect.
Star ground tends to work the best - while balanced technically 'work', and does provide voltage advantage in peak swings, also is more prone to crossover distortion and elevated noise floor.
IMHO, there's no need to reinvent the wheel.
https://benchmarkmedia.com/blogs/application_notes/audio-myth-balanced-headphone-outputs-are-better

http://nwavguy.blogspot.com/2011/05/virtual-grounds-3-channel-amps.html

 

If your D/A/C and amp are unbalanced, then your "balanced" headphones are not really balanced .

 

True, but ultimately, the transducer doesn't "care" if it's fed two inverted signals or one in-phase and ground.

https://benchmarkmedia.com/blogs/application_notes/balanced-vs-unbalanced-analog-interfaces

 

In a balanced set you have twice the voltage in the output to your balanced phones plus reduced sensitivity to external electrical noise. This will increase the headroom and imaging... at least in theory. I would like to try something like this:



And this:



https://www.headphone.com/pages/balanced-headphones-guide

 

Last edited: Mar 21, 2019

Oy vey! Right first of all you need to understand balanced. A non-balanced mono connector uses two connectors, a mono balanced uses at least three and usually fully four.

You understand NULL summing, right? An exact out-of-phase signal completely cancels the in-phase original giving NULL. It's the same idea on cables. You have a common (which is properly seperate from the ground running through the outer braid) the common being one connection. There's the 'hot' side of the signal (the in-phase original) and the cold, the 180 degree out of phase copy signal. That makes three and a ground.



The idea is that if any interference affects the signal in the cable, it will affect both sides, hot and cold, in exactly the same way. So when the hot and cold arrive at the other end, and the cold get phase inverted and summed back over the original, the interference will NULL itelf out.

And it does. Thios invented by a Dude called Clark (IIRC) in the fifties. All balanced connectors carry Pro (not consumer) voltages.



Now these bad boys are not fully balanced, the tip and ring are carrying hot and cold respectively but the sleeve and casing have the common and ground combined. Perfectly adequate in most cases.

 

Last edited by a moderator: Mar 21, 2019

darn, always something new to learn, it freaking never stops...

 

Those are the wisest words I have heard in this Forum. It does not matter for how long you have been an engineer, a producer, an aficionado; everyday there is something to learn. One of my favorite quotes is by Jiddu Krisnamurti:

"There is no end to education. It is not that you read a book, pass an examination, and finish with education. The whole of life, from the moment you are born to the moment you die, is a process of learning."

This Forum is an inextinguishable fountain of information for the novice, as well as the seasoned members. Everyday we ought to thank @SAiNT, @Andrew, @Olymoon and other Mods for making it possible for us to enjoy this ride.

 

That's why, back in the day, if you wanted to be an audio engineer you spent two years doing three things: degaussing tape heads, soldering balanced connectors and listening to the man.

 

You forgot to mention, making coffee and playing waiter.

 

Wow, that brought back an old school memory from the 5th or 6th grade (we're talking decades here); During one of my "elective" class periods I signed up for, I was to help out a teacher and one of my duties was to degauss (she used the age appropriate term demagnetize back then) all the tape recorders she had in the class room. It required me to pass a device over the tape heads. Not sure what she used those recorders for as I wasn't one of her regular students.

 

Got to pay yer dues if you want to record the blues.

 

And fetching the talent her Kumquats.

I did once, on such a shopping errand succeed in getting off with a backing vocalist by saying "You lay!" to her, followed by "Oil Of, one bottle." Life was simpler then.

 

Last edited by a moderator: Jul 27, 2019

So does that mean an unbalanced signal must be a consumer voltage,-10dBV?Or not necessarily ?

 

It can be anything you want as long as you're willing to gamble your hardware on it. It's pro, or it's consumer, or it's run away screaming.