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Are headphone balanced cables snakeoil?

Graph Feppar

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#1
Really... do they even theoreticaly possess any advantage that would make audible difference with 12 year old in anechoic chamber listening to test tones?

I understand benefit of dacs and amps that are internally balanced,there is lot of near field noise coupling going on but is balanced really better for the jack - cable - headphone path? Why not run balanced internally and then convert to single ended at the last stage?

Sadly,there is not much measurement about crosstalk in jacks,I saw just one old thread on Head Fi with some user testing the 1/8" and 1/4" single ended jacks and while the small 3.5mm was bad,the big fat 6.35mm had crosstalk bellow 90db up to 20 KHz.
I know cables can cause crosstalk too but doesnt twisted pair conductor geometry remove this? Especialy if the left and right channel have individual shielding,preferabely with something that also blocks magnetic fields like mu metal foil.

I am considering buying balanced cable but I wonder if this is not just waste of money,even if the improvement would be inaudible,would there even be any measurable improvement at all?Ofcourse amps have different power and impedance out of balanced,but amp side aside,is there any benefit for the signal to travel those 2 meters to my headphone in balanced form?

I also heard of the cable borne noise,but I never noticed it myself,wouldnt balanced cable be just as susceptible to microphonics or is it more immune?
 
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tomchr

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#2
OK, so you have a couple of things going on here. I think you're trying to apply some concepts that relate to differential signalling at line level to your headphone case. Let me see if I can tease that apart. I'll start with line-level signalling between two pieces of equipment and treat the headphone case at the end.
Note that I use the terms single-ended = unbalanced and differential = balanced interchangeably.

Single-ended/unbalanced connections between pieces of equipment (say a DAC and an amplifier) suffer from one problem: Ground impedance. When you connect multiple boxes together, any difference in their ground potential will cause an error current to flow in the ground connection between the boxes. This sets up an error voltage (V = I*R) across the ground impedance. This is a problem because a single-ended/unbalanced input cares about the voltage difference between the signal conductor and ground, so when the ground potential is different between the two pieces of equipment due to the error voltage, the error voltage is treated as signal. For more detail, read Bruno Putzeys' article on the subject: https://www.diyaudio.com/archive/bl...d1460406090-bruno-putzeys-micropre-g-word.pdf

The solution to this is to transmit the signal as a voltage difference between two conductors and leave the ground as a shield. An ideal differential/balanced input only cares about the voltage difference between the two wires in the signal pair. In reality, the voltage on the signal pair has to be within some voltage of ground (common-mode voltage range), but this range is typically determined by the power supply of the differential input, hence, on the order of ±15 V.
Because the differential input only cares about the voltage difference between the two wires in the signal pair, any voltage that is imposed equally on each wire in the pair will be rejected (common-mode rejection, CMRR). This is how a differential input rejects hum, for example. Not there are limits to this. A good differential input will have around 80-100 dB of CMRR, so if you somehow manage to get 1 V of hum injected on to the wires, you'll get 10-100 uV of hum on the output of the differential receiver.
Using a twisted pair further minimizes the hum by ensuring that any electric field that couples to the wire is imposed equally on both conductors. The twisted pair was figured out and patented by Alexander Bell back in 1881 for use in phone systems.
There are some more modern cable configurations that are even better than Bell's original twisted pair. Canare's Star Quad, for example. See demo here:

The bottom line is that differential signalling is a really good way to ensure good signal integrity, in particular in noisy environments. That's why you see differential signalling used in pro setups with long wire runs. It would not surprise me if residential setups are operating with the mains hum just below audible. At least I found subjective improvements in sound quality when I converted to differential signalling on all my gear.

Now for your headphone case: Marketeers have caught onto balanced = good, so now anything "high-end" has to be balanced. "Back in the day" when amplifiers had 1% distortion, you could lower the distortion considerably by converting to a balanced design. I have a few issues with this: 1) You only cancel the even order harmonics (those that many find pleasing to the ear) leaving the odd order harmonics (that many find to sound harsh) in the signal. That doesn't sound like a wise thing to do. 2) Most cancellation circuits, in my experience, end up making the performance worse rather than better. This is especially true at the ultra-low distortion levels of modern opamps. 3) There is really no compelling technical reason to use cancellation schemes to lower the THD as modern parts already deliver THD that's orders of magnitude below audible (OPA1612 0.000015% anyone?)
Now before someone cries, "but THD isn't everything!" ... that's true. THD is not everything. But by improving the THD you usually end up with a lot of other improvements as well (IMD and multi-tone IMD spring to mind).

Where balanced is relevant to the headphone case is for crosstalk or coupling between channels. If you share the ground connection between the two headphone drivers, you will have some of the left channel signal mixing with the right channel signal. Even the shared ground in a 1/4" plug can cause crosstalk. For example, I measure 115 dB channel separation in my HP-1 when using the XLR output and about 95 dB when using the 1/4" output. The difference is due to the shared ground in the 1/4" plug. Now, both are below audible and I've never detected any difference in subjective listening tests, but it is definitely a measurable effect and is backed up by theory (Ohm's Law, to be specific). Both outputs on the HP-1 are single-ended. In the XLR output, I just ground the (-) side of the XLR plug. I see no advantage of a balanced amplifier for reasons outlined above.

So to answer your question: If the only shared ground in the connection from the amp to your headphones is in the 1/4" plug, I doubt you'll notice any difference between 1/4" jack and XLR connections to the headphones.
Now, if you go out and spend $2k on a pair of Super Duper Balanced Bling headphone cables, I guarantee you that you will hear a difference. But that has to do with cognitive psychology and not any difference in the stimulus that reaches your ears. Just make sure you read the manufacturer's marketing babble so you know what to expect and which improvements to hear with the $2k bling cables. ;)

I hope this answers your questions and furthers your understanding.

Tom
 

sergeauckland

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#3
Balanced cabling is definitely not snake-oil on long circuits, say over 10metres and on low level circuits like microphones over any distance or for the rare circuits in high RF fields, such as transmitter sites.

They are definitely snake-oil on headphone feeds where the only possible benefit is a tiny, barely measurable and certainly inaudible amount of crosstalk from the common ground cable, shared between the two channels.

Tom's answer above gives you some figures for the difference in crosstalk between the normal single-ended headphone feed and the balanced.

S.
 

sergeauckland

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#5
Balanced cables are awesome tonearm cables.
I don't know about awesome, but certainly, balanced inputs on phono stages would be very sensible, especially for MC cartridges, which are inherently balanced. MM cartridges less so, especially those where the screening can is connected to one channel, but still the principle applies.

S
 

Panelhead

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#6
I agree on phono, been balanced phono for a while. Phono cartridges are a balanced source by design.
My experience is that balanced cabling is good, even for one meter or less. I used to feel balanced kind of takes the quality of the cable out of the equation.
But found one that seemed worse than all the others, Sommer Goblin. Then one better than all the others, Sommer Carbokab. This is after trying Canare (Benchmark) Gotham, Sommer, and others.
Recently found another than is excellent is either SE or balanced, Sommer SC-Albado. Not sure why, identical cables made with Canare Star Quad, Gotham Star Quad and GAC-3, and Sommer Club Black Zilk do not sound as good. Must be some secret sauce in here.
 

watchnerd

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#7
I don't know about awesome, but certainly, balanced inputs on phono stages would be very sensible, especially for MC cartridges, which are inherently balanced. MM cartridges less so, especially those where the screening can is connected to one channel, but still the principle applies.

S
Awesome meaning "well suited for the technical scenario" -- low voltage, MCs being inherently balanced.
 

Graph Feppar

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#8
tomchr Thank you for great informative post!

One thing in your post that I dont understand is,you say both outputs on your HPA1 are single ended,can you explain to me in detail how is possible for single ended amp to have XLR jack?
 

sergeauckland

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#9
tomchr Thank you for great informative post!

One thing in your post that I dont understand is,you say both outputs on your HPA1 are single ended,can you explain to me in detail how is possible for single ended amp to have XLR jack?
It depends how the XLR is wired. I have used XLRs for unbalanced I/O by using pins 1&2 only, with pin 3 connected to pin 1 or left floating depending on circumstances. The XLR is only a connector. I have even used a single XLR as a stereo unbalanced connector, pin 1 common ground, pin 2 Left, pin 3 right.

S
 

Graph Feppar

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#10
hey everybody,please lets keep this discusion about headphone cables.I understand balanced cables can be good in studio recording and other things,dont know much about phono,not my thing but I want this thread to be about your typical audiophile sitting in front of PC or on chair listening to his headphones,I would like if this thread was about headphone cables only.
 

watchnerd

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#11
hey everybody,please lets keep this discusion about headphone cables.I understand balanced cables can be good in studio recording and other things,dont know much about phono,not my thing but I want this thread to be about your typical audiophile sitting in front of PC or on chair listening to his headphones,I would like if this thread was about headphone cables only.
Sorry, my bad...but the topic, as written, was broad. Didn't know it was only headphones.

BTW, does the typical audiophile listen in front of his PC, over cans, these days?
 

Graph Feppar

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#13
Sorry, my bad...but the topic, as written, was broad. Didn't know it was only headphones.

BTW, does the typical audiophile listen in front of his PC, over cans, these days?
You are right,I have forgotten to write "headphone" into the title.

Well I thought about headphone listening specificaly so obviously,headphone audiophiles listen through "cans".

To be quite honest,I have no idea how most audiophiles of the can type listen music,but I bet its with cable thats on average about 2.5 meter long and I think they dont do yoga at the same time,I think they sit in some comfy chair with not much movement to induce microphonic noise in cable.

The reason I painted this scenario is that I dont think any source of electric interference exists in the short distance from headphones to amp,I understand why its nice to have star quad cable when recording in studio and there is bunch of power supplies and electric cables crossing the signal cable but do you really need it when listening to Tidal sitting in front of PC with amp being within arms reach?

I suspect that this whole balanced cable for headphone thing has been overblown on purpose to sell unnecesary balanced cables.
 
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watchnerd

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#14
You are right,I have forgotten to write "headphone" into the title.

Well I thought about headphone listening specificaly so obviously,headphone audiophiles listen through "cans".

To be quite honest,I have no idea how most audiophiles of the can type listen music,but I bet its with cable thats on average about 2.5 meter long and I think they dont do yoga at the same time,I think they sit in some comfy chair with not much movement to induce microphonic noise in cable.

The reason I painted this scenario is that I dont think any source of electric interference exists in the short distance from headphones to amp,I understand why its nice to have star quad cable when recording in studio and there is bunch of power supplies and electric cables crossing the signal cable but do you really need it when listening to Tidal sitting in front of PC with amp being within arms reach?

I suspect that this whole balanced cable for headphone thing has been overblown on purpose to sell unnecesary balanced cables.
No, common noise rejection isn't really an issue if at arm's length under almost any normal scenario.
 

SIY

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#15
The biggest benefit balanced headphone implementations seem to give is (usually) offering 2x the power, for the rare times when that's actually necessary.
Only if it's differential, and then it's actually 4x the power, since the voltage swing is doubled, and P = V^2/Z.

Balanced =/= differential.
 

tomchr

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#16
Balanced =/= differential.
Balanced == differential. In balanced both sides are driven in opposite phase irrespective of ground. In differential both sides are driven in opposite phase irrespective of ground. Both circuit halves are identical. A differential pair is an example of such a driver (or receiver for that matter).

Pseudo-differential or pseudo-balanced is a single-ended output with an inverter added. You get two outputs in opposite phase, so the output "looks" differential, but each output in the pair is referenced to ground.

I don't know about awesome, but certainly, balanced inputs on phono stages would be very sensible, especially for MC cartridges, which are inherently balanced.
Phono = low signal level, relatively high impedance. Perfect for hum injection. Differential would make good sense there.

tomchr Thank you for great informative post!
You're welcome.

One thing in your post that I dont understand is,you say both outputs on your HPA1 are single ended,can you explain to me in detail how is possible for single ended amp to have XLR jack?
In the HP-1, pins 1 and 3 of the XLR are the left and right channel outputs, respectively. Pins 2 and 4 are grounded. That's a single-ended output.

Tom
 

SIY

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#17
Balanced merely means that impedances are equal on each leg. It does not necessarily mean that voltages are equal and opposite. See, for example, Bill Whitlock's excellent paper, excerpted below:

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.” [3] This, like many explanations in print (some in otherwise respectable books), describes signal symmetry – “equal in voltage but opposite in polarity” – but fails to even mention the single most important feature of a balanced interface. SIGNAL SYMMETRY HAS ABSOLUTELY NOTHING TO DO WITH NOISE REJECTION — IMPEDANCE IS WHAT MATTERS! A good, 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.” [4] The impedances, with respect to ground, of the two lines is what defines an interface as balanced or unbalanced.
 

tomchr

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#18
In that case, we should throw balanced out and use differential. I can think of quite a few circuits that would meet Whitlock's definition of balanced while providing exactly zero CMRR. The whole point of differential signalling is to get the CMRR.

Tom
 

SIY

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#19
And that's exactly what Whitlock demonstrates- it's the equal impedances that matter for CMR. Remember, you can have differential input without the source being antisymmetric with respect to ground- ground is an arbitrary construct.
 

tomchr

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#20
I agree that equal impedances matter. However, simply balancing the impedances does not make two single-ended inputs differential. You actually have to measure the voltage difference for anything to be differential. That's why it's called differential.

Tom
 
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