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A question about true balanced differential design signal paths.

post #1 of 32
Thread Starter 

As the title suggests, I have a question about a true balanced setup.

 

In order to have a fully balanced setup, at what point does everything in the signal path need to be balanced?

 

For example. If I buy an Oppo BPD-95 and use the stereo XLR outs, into a true balanced preamp, and then run that out (via the balanced XLR analog outputs) into a dual differential amplifier, then I know 100% that my signal is a true balanced signal through the entire signal path.

 

For example B, lets say I have the Sony PS3, and run an optical (toslink) cable to an Emotiva XDA-1 fully balanced DAC, and then from the balanced XLR outs into a balanced amp.

 

Would example B still be considered a true balanced signal path since when it gets converted to analog, it is done with a true balanced DAC?

 

Example C. Say I buy a Musical Fidelity V-Link, and run a USB cable to the V-Link, then I run the V-Link into the Emotiva XDA-1 (via either toslink or digital coax), and then the XDA-1 balanced out into a fully balanced amplifier.

 

Would example C (similar to example B, but with a different source of signal origination) be considered a true balanced signal path all the way through?

 

I guess my question comes down to this: In order to have a true differential balanced signal chain from bits (of information) to amplifier, does the source (if digital) need to be "designed from the ground up" to be considered fully balanced, or does that only matter after the conversion from digital to analog?

 

I hope what I am asking makes sense. I am really curious about how this works, and what constitutes a 100% true balanced signal for the ENTIRE length of the signal chain.

 

Thanks.


Edited by painted klown - 5/30/12 at 12:06am
post #2 of 32

Balanced wiring is mainly a method of passing signals around. It doesn't necessarily dictate how a device is designed internally. Lots of single-ended devices are balanced at their inputs and outputs, but unbalanced internally.

 

I'll also mention that the only advantage to balanced connections is they avoid hum and RFI interference caused by ground loops. There's no inherent fidelity advantage, if that's what you're concerned about.

 

--Ethan

post #3 of 32
Quote:

I'll also mention that the only advantage to balanced connections is they avoid hum and RFI interference caused by ground loops. There's no inherent fidelity advantage, if that's what you're concerned about.

 

--Ethan

 

 

Indeed, Mr. Winer. After long toil over this very issue on other forums here, I have limited my viewing to the High End forum and here at Sound Science. What is a reasonable listener to do in the face of so much endlessly repeated ignorance. By the way, I ordered your book on your website last night. Thanks in advance for writing it!

 

There is an esoteric advantage in one or two cases for balanced in non noise busting situations, to produce better numbers that are possibly useful. It can double the input impedance of a power amp for better matching, as in the FirstWatt F1. It can also increase the much sought after voltage swing in some amplifiers for Stax headphones. But the endless listening reports of "revelatory" improvements when rewiring dynamic headphones to balanced are starting to affect my health, thus the avoidance of them. What utter tripe. Hope everyone reads your book before posting such placebo results again.

 

Clark


Edited by Clarkmc2 - 5/31/12 at 3:21am
post #4 of 32

Thanks very much Clark. And you're correct about small potential improvements from balanced wiring. For example, a true bi-polar balanced output (not all are) increases the output voltage by 6 dB, so there's a potential small but real increase in s/n. I wanted to keep my post simple and didn't mention that. Though, as I often point out, the noise floor of recordings is rarely limited by the playback gear. It's usually determined by the ambient noise level in the room where the original recording took place. A CD has a s/n of 96 dB. But find any recording that has a silent place where everyone stops for a moment, then look at that in audio software. The VU meter is usually dancing around -60 or even louder!

 

--Ethan

post #5 of 32
Quote:
Originally Posted by Clarkmc2 View Post


Indeed, Mr. Winer. After long toil over this very issue on other forums here, I have limited my viewing to the High End forum and here at Sound Science. What is a reasonable listener to do in the face of so much endlessly repeated ignorance. By the way, I ordered your book on your website last night. Thanks in advance for writing it!

There is an esoteric advantage in one or two cases for balanced in non noise busting situations, to produce better numbers that are possibly useful. It can double the input impedance of a power amp for better matching, as in the FirstWatt F1. It can also increase the much sought after voltage swing in some amplifiers for Stax headphones. But the endless listening reports of "revelatory" improvements when rewiring dynamic headphones to balanced are starting to effect my health, thus the avoidance of them. What utter tripe. Hope everyone reads your book before posting such placebo results again.

Clark

You don't need to use sbalanced inputs to double the input impedance of an amp.
If the designer wanted a higher input impedance they could just use JFETs in the input stage and ste the input impedance wherever they wanted.
Obviously this is an oversimplification but anyway......the "my headphone sounds better because it is balanced" makes me tongue.gif
post #6 of 32
Quote:
Originally Posted by Chris J View Post


You don't need to use sbalanced inputs to double the input impedance of an amp.
If the designer wanted a higher input impedance they could just use JFETs in the input stage and ste the input impedance wherever they wanted.
Obviously this is an oversimplification but anyway......the "my headphone sounds better because it is balanced" makes me tongue.gif


Generally true, but the F1 (and F1J, the F2, F2J and F3) have only one gain stage. No preceding separate input stage, so the F1s balanced choice is the only option to double the input impedance, if you need that. The F1 and F2 series are the only outstanding choices out there for taking full range speakers to their potential, so this is a choice some listeners have to make, one way or the other. I didn't have to, because the F2J was the best for what I have.

 

As for the plethora of balanced remarks, they made me laugh, then they made me sad, then finally sick of them. I see that in a post and I am done paying any attention to that individual about anything having to do with sound.

post #7 of 32
Quote:
Originally Posted by Clarkmc2 View Post


Generally true, but the F1 (and F1J, the F2, F2J and F3) have only one gain stage. No preceding separate input stage, so the F1s balanced choice is the only option to double the input impedance, if you need that. The F1 and F2 series are the only outstanding choices out there for taking full range speakers to their potential, so this is a choice some listeners have to make, one way or the other. I didn't have to, because the F2J was the best for what I have.

As for the plethora of balanced remarks, they made me laugh, then they made me sad, then finally sick of them. I see that in a post and I am done paying any attention to that individual about anything having to do with sound.

Huh?
The F1 input impedance of 50 kilo ohms is not high enough for some people?
post #8 of 32
Quote:
Originally Posted by Chris J View Post


Huh?
The F1 input impedance of 50 kilo ohms is not high enough for some people?


It would be plenty for me, but that is why I used the phrase "if you need that." As no one has ever gone broke underestimating the intelligence of the America people, owning a FirstWatt does not automatically denote the possession of common sense or high IQ. I could see where match ups with dreadfully designed gear could use all the help they could get, not to mention inappropriate choices. With the F2J, Nelson cautions this:

Quote:
There is another factor as well, which is that the F2J has a lower input impedance than the F2- approximately 25 Kohm, so the F2J is recommended for use with preamps with ordinary to low output resistance – tube preamps without cathode followers will work but will not reap as much benefit at high frequencies.

 

I would guess Papa has dealt with those of lesser wit more than he would have liked to. Just a guess. For me, the 25Kohms is enough. (Or perhaps 10Kohms; Nelson lists this value elsewhere for the F1J and the F2J. The F1 is 100kohms and the F2 is 50Kohms.)

 

Nelson used to end his FirstWatt specs pages with an interesting remark that I think is not out of place in the Sound Science forum. It may be the ultimate warning about expectations in audio. I think Mr. Winer might enjoy it as well.

 

Quote:
This amplifier is a specialty product. There is no representation that the amplifier will make you a happy person.

Or, I might add, one who reads directions before using electronic equipment.


Edited by Clarkmc2 - 5/31/12 at 8:48pm
post #9 of 32
Quote:
Originally Posted by Clarkmc2 View Post


It would be plenty for me, but that is why I used the phrase "if you need that." As no one has ever gone broke underestimating the intelligence of the America people, owning a FirstWatt does not automatically denote the possession of common sense or high IQ. I could see where match ups with dreadfully designed gear could use all the help they could get, not to mention inappropriate choices. With the F2J, Nelson cautions this:

I would guess Papa has dealt with those of lesser wit more than he would have liked to. Just a guess. For me, the 25Kohms is enough. (Or perhaps 10Kohms; Nelson lists this value elsewhere for the F1J and the F2J. The F1 is 100kohms and the F2 is 50Kohms.)

Nelson used to end his FirstWatt specs pages with an interesting remark that I think is not out of place in the Sound Science forum. It may be the ultimate warning about expectations in audio. I think Mr. Winer might enjoy it as well.

Or, I might add, one who reads directions before using electronic equipment.

True,
virtually all loudspeakers are designed to work best with a voltage source, not a current source.
post #10 of 32
Quote:
Originally Posted by painted klown View Post

As the title suggests, I have a question about a true balanced setup.

 

In order to have a fully balanced setup, at what point does everything in the signal path need to be balanced?

 

Thanks.

 

I guess it would really have to start at the DAC chip, most high-end DAC chips use a ladder topology with 2-way current switches, this is why DAC chips have balanced outputs.

 

Now I really don't know much about equipment that is out there on the market because I build most of my gear, but balanced outputs on a DAC does not necessarily have to come from the balanced output on the chip itself, balanced outputs are actually very common in pro audio because balanced line transmission can reduce EMI induced in the signal.

 

A signal can easily be converted form unbalanced to balanced / vice versa using 2 OP-Amps, so you can't really tell unless you know the circuit or the manufacturer tells you that it is.

 

I hope that answers your question.

But personally I do not believe it is worth doing considering that the signal probably has already been unbalanced when recorded and it takes 2x the electronic components to make a balanced system (4 channels basically)

post #11 of 32
Quote:
Originally Posted by b1o2r3i4s5 View Post

 

I guess it would really have to start at the DAC chip, most high-end DAC chips use a ladder topology with 2-way current switches, this is why DAC chips have balanced outputs.

 

Now I really don't know much about equipment that is out there on the market because I build most of my gear, but balanced outputs on a DAC does not necessarily have to come from the balanced output on the chip itself, balanced outputs are actually very common in pro audio because balanced line transmission can reduce EMI induced in the signal.

 

A signal can easily be converted form unbalanced to balanced / vice versa using 2 OP-Amps, so you can't really tell unless you know the circuit or the manufacturer tells you that it is.

 

I hope that answers your question.

But personally I do not believe it is worth doing considering that the signal probably has already been unbalanced when recorded and it takes 2x the electronic components to make a balanced system (4 channels basically)

 

I agree with the rest of your post.........................but........when you print a recording to magnetic tape or save it to a hard drive or whatever, the signal (i.e. music) is not saved as a balanced signal.

post #12 of 32

There is a left channel and a right channel - without a ground, what is there to be balanced in recorded media (in any media)? 

post #13 of 32
Quote:
Originally Posted by liamstrain View Post

There is a left channel and a right channel - without a ground, what is there to be balanced in recorded media (in any media)? 

L, Inverted L, R, Inverted R.

4 channels.
But as far as I know, audio signals are never recorded as balanced.

post #14 of 32

The thing to understand here is that "balanced" is an overloaded term, such that it has two different (but similar) meanings that are often confused or mixed.

 

Balanced in pro audio and signal transmission means that there are 3 lines: positive, inverted, and ground.  This allows the positive signal to be added to the inverse of the inverted signal to cancel out line noise.  It also implies, but does not require, a +4 standard for signal level, which gives an extra 12 or so decibels of audio over the consumer unbalanced standard, which should result in a better signal to background noise ratio for the same content.

 

Balanced in headphone wiring means removing the common ground between the two channels, and replacing it with separate grounds that carry the inverted signal.  This is believed to decrease channel crosstalk, and therefore increase stereo separation.  Whether that belief is factual is dependent on the two signals being compared.  One thing that is generally true is that balanced amplifiers use high end designs, and generally sound really good, though it is arguable whether any of this goodness is actually due to having balanced outputs.

 

(My apologies to people in this thread who already know this stuff.  I thought having a clarification may be useful for some.)

post #15 of 32
Quote:
Originally Posted by b1o2r3i4s5 View Post

L, Inverted L, R, Inverted R.

4 channels.
But as far as I know, audio signals are never recorded as balanced.


In digital audio, the inverted channel can be recreated by simply inverting the waveform such that all points are on the opposite side of a sine wave.  So there is no reason to record it separately.  In analog audio, the inverted signal can be recreated with a simple inversion circuit, so there's no reason to record it there either.

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