Balanced vs. Unbalanced Inputs

It seems wrong that getting the benefits of running fully balanced should be such an uncertain adventure.

+1 Sure got that right. The point of the standard was/is plug and play.

I never said that center tap would be better for noise rejection (though it absolutely could be).

It would only be truly differential if you center tapped it and connected the shield to the center tap, such that

The parenthetical remark renders the first statement false. A center tap decreases noise rejection, at least at audio frequencies.

The second quote is certainly suspect. There is no attempt to make the connection differential, but to receive the signal properly differential techniques should be used if a high CMRR is to be expected.

Ooooh, I can see that one is going to be controversial. You seem to be saying SQ differences between different cables arise from running single-ended, as most audiophile systems do, and not from the cables themselves.
Is it going too far to draw some further conclusions from that statement:
1. All well-designed cables sound (much) the same in a balanced set-up.
2. Money spent on expensive cables is (largely) wasted in a balanced set-up. Therefore:
3. There are SQ differences due to cables in a single-ended set-up so expenditure on cables can be justified. But if you choose a balanced system, this will gain at least the same SQ improvements as buying expensive cables, but without the extra cost. Pace - I accept in principle it is more costly to build balanced amplifiers than single-ended.


C.  "your equipment must support the standard, AES48; I can tell you that hardly any high end audio gear supports the standard "

Are you saying that some amplifier hardware fitted with XLRs and said by the manufacturer to be 'fully balanced', is not fully balanced and does not support AES48? Presumably XLRs could be put on for show without the correct wiring behind? If this is correct, someone suitably qualified should start naming names.

Yes, cable manufacturers and inexplicably, many audiophiles, don't like to hear this stuff. But there is so much product out there that does not support the standard that there will be plenty of need for exotic balanced interconnect for a long time.


To be clear, I am saying that SQ differences between different cables are audible if there is no termination standard and if there are signal return currents present in the shield. So this can mean both single-ended and balanced, if the latter is improperly executed. Since that happens a lot in high end audio, we have a high end cable industry making expensive balanced line cables! Quite the opposite of how it should work.

Regarding your numbered points:
1), 2), 3) all Yes, if AES48 is observed.
C. Quite a lot of high end audio hardware has XLR connectors and are not balanced at all; the connectors are there for convenience only. Some VTLs and Lamm products are set up this way (examples I have had contact with did not have pin 3 connected to anything in the amplifier; this will introduce a buzz if the source driving that amp meets AES48 as the circuit is incomplete). Other high end audio products have XLR connectors and are fully balanced (such as ARC and mbl) but don't support the standard regardless. The mbl amp I had contact with was balanced because when it was monostrapped, you could then use the XLR input (meaning you needed two of these amps for stereo). This approach causes signal return currents to be present in the shield and results in a very low CMRR, making the connection susceptible to noise pickup and cable construction. The ARC stuff I've had contact with has had fairly high output impedances, preventing the preamp from driving anything less than about 30,000 ohms. The output was two single-ended stages that were driven out of phase with each other. This causes signal return currents to be present in the shield, and the relatively high impedance of the resulting system causes the setup to be sensitive to cable construction.

Where is the empirical evidence of improvement using balanced connections? Any? Any at all? Oh, that's right, because there is none.  

Actually there is and its historical. So here is the history: Before balanced lines were developed, a long distance phone call was really only good to the other side of nearly any given state, and you had to be prepared to yell at the top of your voice to be heard. When balanced lines were introduced, this made transcontinental phone calls possible with greater intelligibility. The recording industry was quick to adapt the technology (in the late 1940s and this is one of the key technologies besides the invention of the tape recorder that ushered in the age of high fidelity.

The whole point of balanced cable operation is to avoid interconnect cable interaction with the sound of the system and if the tenants of the balanced system are followed, it does this very well. This means that to sound right, the cable does not have to be expensive, it simply has to be correct!

Could you clarify this, because in my mind, the point of balanced is, and has always been common mode noise rejection. Good cable construction will of course lead to consistency of noise on both cables ensuring common mode rejection.

Now w.r.t. studio balanced connections, i.e. AES compliant, that is not just about balanced, but a drive/load standard that is low enough impedance to dominate over cable parameters.

Sure. As you can see from its historic legacy, balanced lines were used to increase intelligibility. This is exactly why it made it possible to hang a pair of microphones above an orchestra, and have the tape machine 150 feet away, receiving that mic signal without degradation. Certainly noise rejection is one aspect, but so is the rejection of ground loops (that is why the balanced line system ignores ground).

No, that statement is quite true. A floating source is not the same as a differential source. It would only be truly differential if you center tapped it and connected the shield to the center tap, such that coupling to the cable shield is similar for both conductors. That is not the case for a cartridge.

This statement is a common myth, and being a myth, is false. A center tap degrades the Common Mode Rejection Ratio, on account of the simple fact that no center tap is really centered exactly. For this reason, center taps are never used. This is true of dynamic mics, cartridges, tape heads and any other inductive source including input and output line transformers. 

And than, we gonna “hear “the difference  between the 2: for me RCA is more open: good balance, beautiful placement , detailed and holographic. XLR: gives also a good balance, placement:okay, but the openness is less: “flatter” compared to RCA.  Conclusion: I only used RCA. ( my system: CEC cd-player, Auralic streamer, Metronome Technologie C6 (dac), Daniël Hertz M6L ( préamp) Wavac MD 805 m ( monoblocks) and Ilumnia Magister (speakers)

The problem here is that in order to obtain the benefit of balanced operation, your equipment must support the standard, AES48. Having introduced balanced line operation to high end audio, I can tell you that hardly any high end audio gear supports the standard and so you hear differences, and often degradation. That's a unfortunate because the technology clearly works (which is why all your recordings use it); you'd think audiophiles would be interested in something that prevents interconnect cables from interacting with their audio system. If you've ever heard differences between cables you know what I'm talking about. Imagine all the cables sounding as good as the best you've heard: that is the benefit.

I think I would be a great idea to ask the the great phono cartridge and phono amp designers to clear this up - hopefully they might all agree. Question: precisely how are cartridge and turntable wired to the phono amp to obtain fully balanced operation?

The first balanced line phono section was made by Atma-Sphere Music Systems in 1988 and offered in the first balanced line preamp in 1989. Since the cartridge is already a balanced source, its a matter of getting the signal to the preamp without involving that signal with the ground system (the tonearm tube and turntable). To this end, the plus and minus outputs of the cartridge are tied to pins 2 and 3 of the XLR connection. The tonearm ground then becomes the shield of the interconnect cable and ties to pin 1 of the XLR at the phono input. Since the phono input is balanced, it ignores ground and looks at what is different between pins 2 and 3. In other words, the signal is **received** in the differential domain. In the old days this was done with an input transformer with its primary winding simply tied to pins 2 and 3; the ground is simply the chassis of the preamp. Of course you don't need the transformer, but then you need a differential amplifier at the input of the phono circuit. This can be done with tubes or transistors. This is how our phono preamps work and the signal is kept in the differential domain throughout the preamp.


The tricky bit is that sometimes the tonearm manufacturer does not supply the arm with a removable interconnect cable. But most do, and usually if they don't (Rega comes to mind) it is possible to convert the arm anyway. Back in the old days, turntables like BSR, Dual, Garrard and so on had the tonearm wires exit the arm beneath the plinth where there was a terminal strip that had connections for the 4 cartridge wires plus the tonearm ground. That was where the interconnect cable was attached, so even for those ancient machines its fairly easy to install a balanced line simply by replacing the interconnect cable.

"...A 5-pin DIN connector like on the Linn is a balanced connection. Pin 3 of the connectors becomes the shield of both channels and ties to pin 1 of the XLRs at the other end of the tonearm cable..."

However, the Linn arm cable terminates with RCA not XLR.

@brskie
Yes. Linn chose to use RCAs and bring out pin 3 as a separate connection (the ground wire). But if you run balanced, there is no ground wire because it is ground, which is pin 1 of the XLRs, which are tied to pin 3 of the DIN connector. IOW, you merely change out the interconnect cable.

The ground (shield of both channels of the interconnect cable, pin 3 of the DIN connector) is grounded to the chassis of the phono preamp. In the case of the ARC, it should not contact the sleeve of the RCA connection in any way. But obviously since its tying to chassis, its by definition common to both channels. "

So does this mean that to send a balanced signal to the phono pre I should connect that "weird 3rd ground wire" to the ground post on the ARC, or, should I ignore it and tape over the end so it won't ground to the chassis of some component.

Since ARC chose to use a non-standard connection (an RCA instead of XLR; this was done so you could just plug in a regular single-ended connection and it would still work) the cable you need is a bit confusing.


At the tonearm end its a DIN connection. The cable for one channel needs to have a shield around a twisted pair. The twisted pair will carry the signal. They will tie to the RCA connector at the output. The shield ties to pin 3 of the DIN connector and will have to have a wire attached to it at the other end of the cable with a little bit of length, so it can be tied to the chassis ground post of the preamp. The other channel should be the same thing (so this makes the pin 3 connection of the DIN a bit tricky). The two wires at the output end are then tied together and a lug installed. The lug is then attached to the ground post. Care must be taken in the construction of this cable so that the shield is not able to come in contact with the sleeve of the RCA connectors and also does not tie to anything but pin 3 at the DIN end of the cable. If you have a cable made up like this it will be plug and play with no buzz issues, as long as nothing is touching the RCA connectors when they are plugged in.


We put XLR connections at the input of our phono section so that the end user would be forced to set up the cable correctly. There is no need for an RCA connection if your phono section is balanced; the only reason ARC did this was to make dealers happy so they wouldn't have to change their interconnect cable for the tonearm. The downside of this is that the most important place in the entire system to get the cable right is arguably the tonearm cable- anything that goes wrong at that point can't be made up for downstream!


The whole point of balanced cable operation is to avoid interconnect cable interaction with the sound of the system and if the tenants of the balanced system are followed, it does this very well. This means that to sound right, the cable does not have to be expensive, it simply has to be correct!

RCA connectors can't carry a balanced signal. You need to use cables with XLR connectors to support balanced.

This isn't entirely true. If the sleeve connection is shielded in the interconnect cable independantly of ground, and if the ground connection is in no way allowed to contact the sleeve, then the RCA can transmit a balanced signal, with the only issue being its slightly more capable of hum pickup at the connector itself. In practice this isn't an issue unless you touch it.

Technically a phono cartridge is "floating" which means it's neither balanced or single ended. It can be wired either way but the reason there are so few balanced turntables/phono stages is that there is diminishing return on splitting the signal to make it balanced, particularly when the signal from a cartridge is already so weak. 

This statement is false. A floating inductor like a cartridge is in fact a balanced source. In order to run it single-ended, you have to do something with the grounding system, which is that weird 3rd ground wire that no other single-ended source seems to need. With a balanced source, ground is ignored (the ground wire, which is also the tonearm tube); there's no connection between the source and ground.

You don't have to 'split' the signal. In a balanced system, the floating signal is applied to the inverting and non-inverting inputs of the amplifier or preamplifier. Again, ground is ignored- its only used for shielding and there is no signal current in it.

A 5-pin DIN connector like on the Linn is a balanced connection. Pin 3 of the connectors becomes the shield of both channels and ties to pin 1 of the XLRs at the other end of the tonearm cable.

I can see why there is so much confusion around this topic of balanced/unbalanced signals with the unwillingness of audio companies to follow a strict set of standards.

@brskie  When we made the world's first balanced line preamp (for home use) back in 1989, it didn't occur to us that we should do anything other than meet the standards of balanced line operation, known as AES48. But as balanced line became a thing in high end audio, we found that almost everyone was ignoring or were unaware of the standard. So there is a *ton* of confusion about this topic. 

... while the grounding wire/grounding post becomes the tone arm/turntable chassis ground connection common to BOTH channels?

No. The ground is independent and not common to either channel. 

This is begging for clarification! The ground (shield of both channels of the interconnect cable, pin 3 of the DIN connector) is grounded to the chassis of the phono preamp. In the case of the ARC, it should not contact the sleeve of the RCA connection in any way. But obviously since its tying to chassis, its by definition common to both channels.