Help with balanced audio.

[Swollef]

Hello, I bought a balanced dac by mistake and an unbalanced amp, I have no intention of using balanced audio. I didnt lose any money by buying the balanced model, but I am concerned with quality, the unbalanced dac has a rca hookup whereas the balanced dac has xlr with only 3.5MM for unbal backup. Should I return the dac and get a unbalanced one to do rca to rca or is 3.5mm to RCA fine for quality (this is a budget setup).

[Behexen250]

You don't say what DAC you have, but you state its a budget system. Given that, your DAC is probably not balanced. Here's how you can tell. Balanced and single ended components are not compatible. Its either one or the other. If your DAC really is balanced, there has to be a way to switch between the xlr jacks and the 3.5mm jack. It may be some type of switch, or you may have to put a jumper in your xlr jacks, but the main thing is that you will have to switch the DAC to operate in un-balanced mode in order to use the 3.5mm. If there's no switch, then your DAC is not balanced. If so, your best option would be to get xlr to rca converters, and just use a regular pair of un-balanced interconnects. 

 

If you are new to this and are surprised that I'm telling you your DAC isn't balanced, its true. A lot of components are made to look like they are really balanced when they're not.    

[GregWormald]

The only way to really tell is to listen to both.

 

Other than for long runs, or in electrically noisy environments there is no real advantage to balanced cables. Of course how the manufacturer generates the balanced or the unbalanced outputs may have some influence on quality.

 

You should be fine—but how hard is it to return for RCA-RCA? They are the most popular cables for home stereo.

[lucretius]

Assuming the 3.5mm jack is "line out", then 3.5mm (out) to RCA (input on amp) will be fine for quality. 

[bluesman]

3 hours ago, Behexen250 said:

If your DAC really is balanced, there has to be a way to switch between the xlr jacks and the 3.5mm jack. It may be some type of switch, or you may have to put a jumper in your xlr jacks, but the main thing is that you will have to switch the DAC to operate in un-balanced mode in order to use the 3.5mm.

That's not correct.  Many DACs have balanced and unbalanced outputs that are both active and require no switching of any kind to use either one.  I have two (Emotiva Stealth DC-1 and SMSL SU-8).  If you like the DAC you bought, just buy $8 adapter cables like this one

 

 

to convert your balanced output to an unbalanced line signal you can plug into your amplifier.  Even if Behexen250 were correct that your DAC is not really balanced (which I strongly doubt, assuming you read the specs and descriptive info carefully), these cables will do the job fine for you.  

 

That 1/8" TRS jack may well be a headphone jack, rather than a line out.  Many audio cards, interfaces etc for gamers and for recording have 1/8" or 1/4" line outs, but the unbalanced line outs on almost all DACs intended for use in audio systems are RCA jacks.  I've never seen a DAC sold for home audio use with a single stereo 1/8" TRS line out jack.

[Behexen250]

54 minutes ago, bluesman said:

That's not correct.  Many DACs have balanced and unbalanced outputs that are both active and require no switching of any kind to use either one.  I have two (Emotiva Stealth DC-1 and SMSL SU-8).  If you like the DAC you bought, just buy $8 adapter cables like this one

 

 

to convert your balanced output to an unbalanced line signal you can plug into your amplifier.  Even if Behexen250 were correct that your DAC is not really balanced (which I strongly doubt, assuming you read the specs and descriptive info carefully), these cables will do the job fine for you.  

 

That 1/8" TRS jack may well be a headphone jack, rather than a line out.  Many audio cards, interfaces etc for gamers and for recording have 1/8" or 1/4" line outs, but the unbalanced line outs on almost all DACs intended for use in audio systems are RCA jacks.  I've never seen a DAC sold for home audio use with a single stereo 1/8" TRS line out jack.

I don't know why you are getting so upset, but I'm not wrong. There are countless audio components that are labeled balanced when they are not. Its a problem in the industry that's been going on for years. For example, its a fairly common practice to put xlr connectors on a single ended component, and label it balanced. When you read the fine print in the manual, it says you can use balanced cables, and you can. 2 of the 3 pins get used, and its identical to using a pair of rca cables. I remember a few years back Stereophile called out Rotel for doing this on one of their amps. 

 

With regards to how it works, you can not connect a balanced component to a single ended component. Something has to be done to either convert the signal or change the operation of one of the components. Otherwise, you are crossing wires. You will get a terrible noise and possibly damage your equipment. In the pro audio world, its customary to use direct boxes to convert any un-balanced signals to balanced, making it compatible with studio/house system gear. With home audio, its customary to switch components from balanced to SE operation because cable length and noise is not as big a factor in home systems. 

 

As for your Emotiva component having 2 active outputs, I hadn't thought about that, to be honest. But it really doesn't change anything. All the same rules still apply. Emotive is doing this as a convenience. If you take the active balanced outputs and connect it to a SE components with adaptors, you'll have a problem. Most components are not set up like this, so you need to be careful.

 

In the future, if you have an issue with anything I say, just ask me to clarify it. There's really no reason to get upset. 

[PeterG]

I have a Schiit Yggdrasil that the manufacturer swears sounds best in balanced mode when headed into a balanced preamp, which I have.  I've had great success upgrading cables for better sound, ending up with Transparent Super interconnects.  But I cannot hear the difference between balanced and unbalanced from the Yggy.  So I would not sweat this

[bluesman]

2 hours ago, Behexen250 said:

There's really no reason to get upset. 

I’m not upset. But I imagine that the OP was probably quite upset when you told him that he didn’t get what he thought he did.  He asked for assistance, not a slap in the face.
 

Newbies need and deserve help and reassurance, .  Maybe he was sold a DAC as balanced when it isn’t.  If so, he should know this.  But your unqualified statement that “your DAC is probably not balanced” is both unfounded and harsh.  And telling him that a balanced DAC has to have some kind of switch between outputs is simply wrong.  
 

The OP deserves a better understanding than you offered him.  He states that the same DAC (and I too would like to know which one it is) is available with balanced and unbalanced outputs.  Since he isn’t running a balanced system, it doesn’t matter if it is or isn’t. What he needs is advice on the simplest, least expensive way to make his system work. Properly wired XLR-to-RCA cables solve the problem either way.

 

You can connect a balanced output to an unbalanced input. This document from Rane explains it well and offers several options.  An occasional hookup is problematic, but it usually works fine.  I’ve been doing it for decades on stage and in the studio.  But the wiring of that cable is not the same for balanced XLR to unbalanced rca as it is for unbalanced XLR to unbalanced rca.

 

I’m sorry you took umbrage at my response - but I hope you’ll give a bit more consideration to the needs and feelings of a newbie before telling him he was misled.  Your belief that...

 

2 hours ago, Behexen250 said:

you can not connect a balanced component to a single ended component

 

is incorrect, as is your belief that the DAC in question can’t possibly have balanced outputs because it has no switch to select outputs.  I simply do not want to see a novice misinformed.

[Behexen250]

16 hours ago, bluesman said:

I’m not upset. But I imagine that the OP was probably quite upset when you told him that he didn’t get what he thought he did.  He asked for assistance, not a slap in the face.
 

Newbies need and deserve help and reassurance, .  Maybe he was sold a DAC as balanced when it isn’t.  If so, he should know this.  But your unqualified statement that “your DAC is probably not balanced” is both unfounded and harsh.  And telling him that a balanced DAC has to have some kind of switch between outputs is simply wrong.  
 

The OP deserves a better understanding than you offered him.  He states that the same DAC (and I too would like to know which one it is) is available with balanced and unbalanced outputs.  Since he isn’t running a balanced system, it doesn’t matter if it is or isn’t. What he needs is advice on the simplest, least expensive way to make his system work. Properly wired XLR-to-RCA cables solve the problem either way.

 

You can connect a balanced output to an unbalanced input. This document from Rane explains it well and offers several options.  An occasional hookup is problematic, but it usually works fine.  I’ve been doing it for decades on stage and in the studio.  But the wiring of that cable is not the same for balanced XLR to unbalanced rca as it is for unbalanced XLR to unbalanced rca.

 

I’m sorry you took umbrage at my response - but I hope you’ll give a bit more consideration to the needs and feelings of a newbie before telling him he was misled.  Your belief that...

 

 

is incorrect, as is your belief that the DAC in question can’t possibly have balanced outputs because it has no switch to select outputs.  I simply do not want to see a novice misinformed.

Misinformed? I can't imagine anyone more misinformed than you. You don't know a thing about audio. You're an expert internet poster, and nothing more. 

 

You want to quote me? "you can not connect a balanced component to a single ended component"

 

You're damn right you can't. Anyone who says otherwise is clueless, and has no idea how balancing works. If you want to prove me wrong, simply pick 2 pieces of equipment, one that runs in balanced operation, and the other SE, and explain how you would connect them. 

 

Aside from that, you are just plain lying.

 

"

Your belief that...

is incorrect, as is your belief that the DAC in question can’t possibly have balanced outputs because it has no switch to select outputs.  I simply do not want to see a novice misinformed."

 

You pick the quote apart to suit your needs. My real statement was that if you have balanced and SE labeled connections on the DAC and have no way to switch between them, be it a switch, a jumper on the xlr jack, or any other means, its not balanced. You brought up an instance I didn't consider in that the component can have 2 active, independent outputs and technically wouldn't need to switch. So, aside from your rare exception on the Emotiva piece, my statement is 100% accurate. Without a way to switch, it can't be balanced. Quote me 100 times on it, because its right. 

 

The silly part is, anyone who has a passing interest in this topic can just look it up.

 

 

[bluesman]

4 hours ago, Behexen250 said:

Misinformed? I can't imagine anyone more misinformed than you. You don't know a thing about audio. You're an expert internet poster, and nothing more......Aside from that, you are just plain lying.

 

My real statement was that if you have balanced and SE labeled connections on the DAC and have no way to switch between them, be it a switch, a jumper on the xlr jack, or any other means, its not balanced. You brought up an instance I didn't consider in that the component can have 2 active, independent outputs and technically wouldn't need to switch. So, aside from your rare exception on the Emotiva piece, my statement is 100% accurate. Without a way to switch, it can't be balanced.

Wow, Behexen250 - it's clear that you know everything you want to know, so I won't insult you further with my inferior knowledge.  I will not respond to you again.  Please show me the same courtesy and do not insult me with a response to this.  You're welcome to believe that I'm ignorant, an impostor, and anything else that makes you feel better.  Your thoughts are well understood and you're fully entitled to them - you do not need to repeat yourself.

 

For the OP and those who do want to know more, let's start with the simple fact that "balanced" and "unbalanced" are not synonyms for "single ended" and "double ended".  Balanced inputs and outputs do not define the circuitry to which they provide access, and many single ended amplifiers have true balanced inputs and outputs.  It's easy to turn a single ended line output signal into a balanced output by adding an inverting buffer stage to generate a parallel signal 180 degrees out of phase with the preamplifier's output.  This will yield the benefits of a balanced connection (noise rejection, low loss over long lengths, etc).  A balanced output created this way is truly balanced and will drive a fully differential amplifier ("FDA", in industry parlance) through a true balanced input.  Of course, an FDA can accept and drive both balanced and unbalanced inputs and outputs, but most low and mid level consumer audio equipment is not based on fully differential circuitry.

 

Many of our preamps and amps have true balanced inputs and/or outputs but use single ended circuitry in between.  And an amp can have unbalanced (single ended, common ground) input but use balanced push-pull amplification that provides both balanced and single ended outputs.  An unbalanced single-ended input has one conductor for the signal and a second conductor serving as a common ground. An unbalanced differential input requires positive and negative input signals, so it has two conductors plus ground.  But it's still an unbalanced line despite having 3 conductors and an XLR on the end, because the resistances between the positive signal to ground and the negative signal to ground are not matched (which is the definition of balanced in this application).

 

For specific wiring instructions when connecting unbalanced and balanced components, I again refer you to that excellent Rane document (which has been the industry reference on balanced / unbalanced interconnects for 35 years) and to this support page at Sweetwater (a major vendor of musical equipment and pro recording equipment). The Sweetwater page is entitled "Balanced Outputs Connected to Unbalanced Inputs" and was written to help the many customers who have balanced and unbalanced equipment in their studios and systems.  You absolutely can connect unbalanced line outputs to balanced amplifier inputs and vice versa.  You usually lose the benefits of balanced circuitry, e.g. common mode noise rejection, long lines etc.  So SQ is most often no better than that from using unbalanced, single ended interconnects on the same electronics.

 

Regarding multiple output modes, my Emotiva is hardly a rare exception.  Most balanced DACs from about $200 to about $2000 have both XLR balanced outputs and RCA unbalanced outputs that require no switching between them.   Here are just a few popular examples:

 

Mytek Manhattan:  

 

Schiit Yggy: 

 

Cambridge DacMagic: 

 

Schiit Bifrost: 

 

SMSL M100: 

 

Topping DX7: 

 

Topping D70:  

 

SMSL SU8:  

 

And almost all pro quality recording electronic equipment aimed at serious amateurs and smaller studios is set up and delivered with both balanced and unbalanced access.  The Golden Age PRE-73 DLX is a classic example of a wonderful, well priced studio preamp with true, transformer balanced I/O and simultaneously active balanced and unbalanced line outs.  The input jacks are combination balanced / unbalanced - the center hole is a 1/4" phone jack.

 

 

It's a single channel unit that now costs about ($600 IIRC) with the best Carnhill transformers, an option well worth getting - these are the same transformers used in the great Neve preamps.

 

[Behexen250]

32 minutes ago, bluesman said:

Wow, Behexen250 - it's clear that you know everything you want to know, so I won't insult you further with my inferior knowledge.  I will not respond to you again.  Please show me the same courtesy and do not insult me with a response to this.  You're welcome to believe that I'm ignorant, an impostor, and anything else that makes you feel better.  Your thoughts are well understood and you're fully entitled to them - you do not need to repeat yourself.

 

For the OP and those who do want to know more, let's start with the simple fact that "balanced" and "unbalanced" are not synonyms for "single ended" and "double ended".  Balanced inputs and outputs do not define the circuitry to which they provide access, and many single ended amplifiers have true balanced inputs and outputs.  It's easy to turn a single ended line output signal into a balanced output by adding an inverting buffer stage to generate a parallel signal 180 degrees out of phase with the preamplifier's output.  This will yield the benefits of a balanced connection (noise rejection, low loss over long lengths, etc).  A balanced output created this way is truly balanced and will drive a fully differential amplifier ("FDA", in industry parlance) through a true balanced input.  Of course, an FDA can accept and drive both balanced and unbalanced inputs and outputs, but most low and mid level consumer audio equipment is not based on fully differential circuitry.

 

Many of our preamps and amps have true balanced inputs and/or outputs but use single ended circuitry in between.  And an amp can have unbalanced (single ended, common ground) input but use balanced push-pull amplification that provides both balanced and single ended outputs.  An unbalanced single-ended input has one conductor for the signal and a second conductor serving as a common ground. An unbalanced differential input requires positive and negative input signals, so it has two conductors plus ground.  But it's still an unbalanced line despite having 3 conductors and an XLR on the end, because the resistances between the positive signal to ground and the negative signal to ground are not matched (which is the definition of balanced in this application).

 

For specific wiring instructions when connecting unbalanced and balanced components, I again refer you to that excellent Rane document (which has been the industry reference on balanced / unbalanced interconnects for 35 years) and to this support page at Sweetwater (a major vendor of musical equipment and pro recording equipment). The Sweetwater page is entitled "Balanced Outputs Connected to Unbalanced Inputs" and was written to help the many customers who have balanced and unbalanced equipment in their studios and systems.  You absolutely can connect unbalanced line outputs to balanced amplifier inputs and vice versa.  You usually lose the benefits of balanced circuitry, e.g. common mode noise rejection, long lines etc.  So SQ is most often no better than that from using unbalanced, single ended interconnects on the same electronics.

 

Regarding multiple output modes, my Emotiva is hardly a rare exception.  Most balanced DACs from about $200 to about $2000 have both XLR balanced outputs and RCA unbalanced outputs that require no switching between them.   Here are just a few popular examples:

 

Mytek Manhattan:  

 

Schiit Yggy: 

 

Cambridge DacMagic: 

 

Schiit Bifrost: 

 

SMSL M100: 

 

Topping DX7: 

 

Topping D70:  

 

SMSL SU8:  

 

And almost all pro quality recording electronic equipment aimed at serious amateurs and smaller studios is set up and delivered with both balanced and unbalanced access.  The Golden Age PRE-73 DLX is a classic example of a wonderful, well priced studio preamp with true, transformer balanced I/O and simultaneously active balanced and unbalanced line outs.  The input jacks are combination balanced / unbalanced - the center hole is a 1/4" phone jack.

 

 

It's a single channel unit that now costs about ($600 IIRC) with the best Carnhill transformers, an option well worth getting - these are the same transformers used in the great Neve preamps.

 

After all that you go and cut and paste stuff out of a book. You don't even realize what you're saying. 

 

"You absolutely can connect unbalanced line outputs to balanced amplifier inputs and vice versa.  You usually lose the benefits of balanced circuitry, e.g. common mode noise rejection, long lines etc.  So SQ is most often no better than that from using unbalanced, single ended interconnects on the same electronics."

 

That's the point genius. Its not balanced when you do it that way. Its in your own words and you don't even understand it.

 

For anyone who's interested and doesn't want to read through a bunch of crap put in a post to make someone look smart, here it is. A single ended connection has 2 conductors. Signal and ground. Usually represented as + and -. As you can imagine, if you stripped the connector off to bare wires, it wouldn't be a good idea to cross them when electricity is flowing through them. Balanced operation adds a 2nd signal out of polarity with the original, on the 3rd conductor. You would never want to cross either if these signal wires with ground. That's why you can't, under any circumstances, plug a balanced signal directly into a SE component. It literally can't work. All the pointless examples listed above are different variations and examples of balanced operation. It doesn't matter which one you use, the rules of mixing components don't change. 

 

I also don't know what the obsession is with Rane. I'm a DJ and own some of their gear myself. I have a 72 and 2 12's. Very few people reading this are going to be using their gear. Its equipment that's primarily meant for use in night clubs. I guess you can use them as an example, but the reason and method of why they balance, may not be the same as someone putting together a home stereo.

 

The original post implied a budget system. My point was that a budget dac may not be balanced even though it may look that way. If you don't want to take my word for it, here's what Benchmark has to say. We all know who they are, and some of the people reading this will actually own some of their gear. 

 

"

There are some consumer products that have "balanced" inputs with a CMRR of 0 dB. Let's just call these "fake" balanced inputs. The input is equipped with an XLR connector, but the - pin (pin 3) is ignored. These are just unbalanced inputs wired to an XLR connector. They offer no advantage over unbalanced RCA inputs. In most cases, pin 2 of the XLR is tied directly to the center contact of a nearby RCA input. This makes the XLR jack nothing more than an adapter.

There are other devices that use the + and the - pins, but they fail to remove common mode noise before the signal leaves through a balanced output. These devices simply pass the common mode noise on to the next component in hopes that the next component will remove the common mode noise. If you can't find a specification for CMRR, the balanced input may not have a differential amplifier. If this is the case, the input is just a pair of unbalanced inputs feeding a pair of unbalanced outputs."

 

Here's a link to the full post. Are they making stuff up as well?

 

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

 

[Audiophile Neuroscience]

2 hours ago, bluesman said:

Balanced inputs and outputs do not define the circuitry to which they provide access, and many single ended amplifiers have true balanced inputs and outputs.  It's easy to turn a single ended line output signal into a balanced output by adding an inverting buffer stage to generate a parallel signal 180 degrees out of phase with the preamplifier's output. 

 

 

1 hour ago, Behexen250 said:

After all that you go and cut and paste stuff out of a book. You don't even realize what you're saying. 

 

"You absolutely can connect unbalanced line outputs to balanced amplifier inputs and vice versa.  You usually lose the benefits of balanced circuitry, e.g. common mode noise rejection, long lines etc.  So SQ is most often no better than that from using unbalanced, single ended interconnects on the same electronics."

 

That's the point genius. Its not balanced when you do it that way. Its in your own words and you don't even understand it.

 

For anyone who's interested and doesn't want to read through a bunch of crap put in a post to make someone look smart, here it is. A single ended connection has 2 conductors. Signal and ground. Usually represented as + and -. As you can imagine, if you stripped the connector off to bare wires, it wouldn't be a good idea to cross them when electricity is flowing through them. Balanced operation adds a 2nd signal out of polarity with the original, on the 3rd conductor.

 

 

gentleman, I am out of my wheelhouse here so please be kind. The whole balanced and differential thing has confused me for decades. I know my amplifier manufacturer goes to great pains to point out that it is truly balanced and fully differential (or words to that effect). In an effort to educate people like myself and for that matter help guide the OP in his question it would be helpful to get to the bottom of all of this.

 

I do wonder whether both of you just may be be talking about circuit symmetry/polarity rather than, or as well as, balanced interfaces. I stress I wonder, not claim.

 

I usually go to Uncle Bill for such matters (Bill Whitlock). I again wonder whether his explanations are most aligned with your views?

 

QUOTE

 

An interface may be unbalanced or balanced, depending only on the impedances (to ground) of the line's conductors.

 

In balanced interfaces, both conductors have equal (and non-zero) impedances. A balanced interface requires that driver, line, and receiver all maintain balanced impedances to ground. Balanced interfaces are extremely potent in preventing all kinds of noise coupling. In fact, it's so powerful that many systems, such as telephone systems, use it instead of shielding as the main noise reduction technique!

 

 A QUESTION OF BALANCE

The true nature of balanced interfaces is widely misunderstood. For example "Each conductor is always equal in voltage but opposite in polarity to the other. The circuit that receives this signal in the mixer is called a differential amplifier and this opposing polarity of the conductors is essential for its operation. "  This, like many explanations in print, describes signal symmetry (i.e.,"equal in voltage but opposite in polarity") but completely overlooks the most important feature of a balanced interface.

 

The notion that signal symmetry has anything to do with noise rejection is

simply WRONG! Quoting a part of the informative annex of IEC Standard 60268-3: "Therefore, only the common-mode impedance balance of the dnver, line, and receiver play a role in noise or interference rejection. This noise or interference rejection property is independent of the presence of a desired differential signal. Therefore, it can make no difference whether the desired signal exists entirely on one line, as a greater voltage on one line than the other, or as equal voltages on both of them.

 

 Symmetry of the desired signal has advantages, but they concern headroom and

crosstalk, not noise or interference rejection. "

 

An accurate definition is "A balanced circuit is a two-conductor circuit in which both conductors and all circuits connected to them have the same impedance with respect to ground and to all other conductors. The purpose of balancing is to make the noise pickup equal in both conductors, in which case it will be a common-mode signal which can be made to cancel out in the load. "

 

 A simplified balanced interface is shown in the schematic.

 

 

Theoretically, it can reject any interference, whether due to ground voltage differences, magnetic fields, or electric fields, as long as it produces identical voltages each of the signal lines and the resulting peak voltages don't exceed receiver capability. When both devices are grounded to the safety ground system, the ground voltage difference between them becomes the "ground noise" shown. When one or both devices is ungrounded, the ground voltage difference can become very large. Traditionally, balanced audio interconnects use shielded cable with each end of the shield connected to respective device ground. This connection serves to minimize the ground voltage difference between the devices.

 

However, if such a connection is absent, other measures may be required to limit the ground voltage difference. The voltage that appears identically on both inputs, since it is common to both inputs, is called the common-mode voltage.

 

A balanced receiver uses a differential device, either a specialized amplifier or a transformer, which inherently responds only to the voltage difference between its inputs. An ideal receiver would have no response to common-mode voltages. But with real devices, the response is not zero. The ratio of the device's differential gain to its common-mode gain is called its common-mode rejection ratio, or CMRR. It's usually expressed in dB, where higher numbers mean better rejection. Note that the common-mode (i.e., with respect to ground) output impedances of the driver and input  impedances of the receiver effectively form a Wheatstone bridge as shown.

 

If the bridge is not balanced or nulled, a portion of the ground noise Vcm will be converted to a differential signal on the line. The nulling of the common-mode voltage is critically dependent on the ratio matching of these pairs of Vcm driver/receiver common-mode impedances. The nulling is relatively unaffected by impedance across the lines — only the common-mode impedances matter!

 

The bridge is most sensitive to small fractional impedance changes in one of its arms when all arms have the same impedance.  It is least sensitive when upper and lower arms have widely differing impedances. Therefore, we can minimize the CMRR degradation in a balanced interface caused by normal component tolerances by making common-mode impedances very low at one end of the line and very high at the other.  The output impedances of virtually all real line drivers are determined by series resistors (and often coupling capacitors) that typically have + or - 5% tolerances. Because of this, typical drivers can have output impedance imbalances in the vicinity of 10 Q. The common-mode input impedances of typical balanced input circuits is in the 10 kOhms to 50 kQ range, making its CMRR exquisitely sensitive to normal imbalances in driver output

impedance. For example, the CMRR of the widely used SSM-2141 will degrade some 25 dB with only one ohm  imbalance. Devices such as input transformers or the InGenius@ balanced receiver IC, are essentially unaffected by imbalances as high as several hundred ohms because since their common-mode input impedances are about 50 MOhms — over 1000 times higher than ordinary "active" inputs.

 

Noise rejection in a real-world balanced interface is often far less than that touted for the

input. That's because the performance of balanced inputs have traditionally been measured in ways that ignore the effects of driver and cable impedances. For example, the old IEC method essentially "tweaked" the driving source impedance until it had zero imbalance. Another method, which simply ties the two inputs together and is still used by many engineers, is equally unrealistic. This author is quite pleased to have persuaded the IEC to adopt a new CMRR test that inserts realistic impedance imbalances in the driving source. The new test is included in the third edition of IEC Standard 60268-3, Sound System Equipment - Part 3: Amplifiers, August 2000. It's very important to understand that noise rejection in a balanced interface isn't just a function of the receiver — actual performance in a real system depends on how the driver, cable, and receiver interact.

[Behexen250]

On 10/2/2020 at 8:20 PM, Audiophile Neuroscience said:

 

 

gentleman, I am out of my wheelhouse here so please be kind. The whole balanced and differential thing has confused me for decades. I know my amplifier manufacturer goes to great pains to point out that it is truly balanced and fully differential (or words to that effect). In an effort to educate people like myself and for that matter help guide the OP in his question it would be helpful to get to the bottom of all of this.

 

I do wonder whether both of you just may be be talking about circuit symmetry/polarity rather than, or as well as, balanced interfaces. I stress I wonder, not claim.

 

I usually go to Uncle Bill for such matters (Bill Whitlock). I again wonder whether his explanations are most aligned with your views?

 

QUOTE

 

An interface may be unbalanced or balanced, depending only on the impedances (to ground) of the line's conductors.

 

In balanced interfaces, both conductors have equal (and non-zero) impedances. A balanced interface requires that driver, line, and receiver all maintain balanced impedances to ground. Balanced interfaces are extremely potent in preventing all kinds of noise coupling. In fact, it's so powerful that many systems, such as telephone systems, use it instead of shielding as the main noise reduction technique!

 

 A QUESTION OF BALANCE

The true nature of balanced interfaces is widely misunderstood. For example "Each conductor is always equal in voltage but opposite in polarity to the other. The circuit that receives this signal in the mixer is called a differential amplifier and this opposing polarity of the conductors is essential for its operation. "  This, like many explanations in print, describes signal symmetry (i.e.,"equal in voltage but opposite in polarity") but completely overlooks the most important feature of a balanced interface.

 

The notion that signal symmetry has anything to do with noise rejection is

simply WRONG! Quoting a part of the informative annex of IEC Standard 60268-3: "Therefore, only the common-mode impedance balance of the dnver, line, and receiver play a role in noise or interference rejection. This noise or interference rejection property is independent of the presence of a desired differential signal. Therefore, it can make no difference whether the desired signal exists entirely on one line, as a greater voltage on one line than the other, or as equal voltages on both of them.

 

 Symmetry of the desired signal has advantages, but they concern headroom and

crosstalk, not noise or interference rejection. "

 

An accurate definition is "A balanced circuit is a two-conductor circuit in which both conductors and all circuits connected to them have the same impedance with respect to ground and to all other conductors. The purpose of balancing is to make the noise pickup equal in both conductors, in which case it will be a common-mode signal which can be made to cancel out in the load. "

 

 A simplified balanced interface is shown in the schematic.

 

 

Theoretically, it can reject any interference, whether due to ground voltage differences, magnetic fields, or electric fields, as long as it produces identical voltages each of the signal lines and the resulting peak voltages don't exceed receiver capability. When both devices are grounded to the safety ground system, the ground voltage difference between them becomes the "ground noise" shown. When one or both devices is ungrounded, the ground voltage difference can become very large. Traditionally, balanced audio interconnects use shielded cable with each end of the shield connected to respective device ground. This connection serves to minimize the ground voltage difference between the devices.

 

However, if such a connection is absent, other measures may be required to limit the ground voltage difference. The voltage that appears identically on both inputs, since it is common to both inputs, is called the common-mode voltage.

 

A balanced receiver uses a differential device, either a specialized amplifier or a transformer, which inherently responds only to the voltage difference between its inputs. An ideal receiver would have no response to common-mode voltages. But with real devices, the response is not zero. The ratio of the device's differential gain to its common-mode gain is called its common-mode rejection ratio, or CMRR. It's usually expressed in dB, where higher numbers mean better rejection. Note that the common-mode (i.e., with respect to ground) output impedances of the driver and input  impedances of the receiver effectively form a Wheatstone bridge as shown.

 

If the bridge is not balanced or nulled, a portion of the ground noise Vcm will be converted to a differential signal on the line. The nulling of the common-mode voltage is critically dependent on the ratio matching of these pairs of Vcm driver/receiver common-mode impedances. The nulling is relatively unaffected by impedance across the lines — only the common-mode impedances matter!

 

The bridge is most sensitive to small fractional impedance changes in one of its arms when all arms have the same impedance.  It is least sensitive when upper and lower arms have widely differing impedances. Therefore, we can minimize the CMRR degradation in a balanced interface caused by normal component tolerances by making common-mode impedances very low at one end of the line and very high at the other.  The output impedances of virtually all real line drivers are determined by series resistors (and often coupling capacitors) that typically have + or - 5% tolerances. Because of this, typical drivers can have output impedance imbalances in the vicinity of 10 Q. The common-mode input impedances of typical balanced input circuits is in the 10 kOhms to 50 kQ range, making its CMRR exquisitely sensitive to normal imbalances in driver output

impedance. For example, the CMRR of the widely used SSM-2141 will degrade some 25 dB with only one ohm  imbalance. Devices such as input transformers or the InGenius@ balanced receiver IC, are essentially unaffected by imbalances as high as several hundred ohms because since their common-mode input impedances are about 50 MOhms — over 1000 times higher than ordinary "active" inputs.

 

Noise rejection in a real-world balanced interface is often far less than that touted for the

input. That's because the performance of balanced inputs have traditionally been measured in ways that ignore the effects of driver and cable impedances. For example, the old IEC method essentially "tweaked" the driving source impedance until it had zero imbalance. Another method, which simply ties the two inputs together and is still used by many engineers, is equally unrealistic. This author is quite pleased to have persuaded the IEC to adopt a new CMRR test that inserts realistic impedance imbalances in the driving source. The new test is included in the third edition of IEC Standard 60268-3, Sound System Equipment - Part 3: Amplifiers, August 2000. It's very important to understand that noise rejection in a balanced interface isn't just a function of the receiver — actual performance in a real system depends on how the driver, cable, and receiver interact.

I get all that. My response to the OP was to make sure his dac is really balanced, and not a single ended component with xlr jacks. 

 

My argument with bluesman was over the mixing of balanced and SE components. It doesn't matter what type balancing a component has. You can't connect the 2. There's just no way around it. You either have to convert a SE signal to balanced, or a balanced signal to SE, in order for them to work. Also, it was foolish of me not to fact check him. I took him at his word that Emotiva, and some other brands have some new feature that lets both type of connections to work actively at the same time, and not have to switch between the two. I went over to Emotiva's web site and got this right out of a user manual.

 

"A high-quality metal toggle switch independently selects between the Unbalanced (RCA) and Balanced (XLR) input for each channel. Up selects the Unbalanced input and Down selects the Balanced input. Only one input can be used at once for each channel. (Both a balanced and an unbalanced source may be connected at the same time, and the switch used to select between them, but only one will be active at any given time.)"

 

The guy's a joke and shouldn't be allowed to post. He says the exact opposite just to win the argument, and claims he's trying to give the OP the right information. Garbage like this is what makes so many people walk away from audio in frustration.