Single 4 Pin XLR headphone cable is balanced, huh?

[scolley]

Apologies in advance for a long OP. But there are a lot of conflicting data points here, leading to some confusion (and ignorance) on my part that I'm hoping someone will be able to clear up.

 

I’m no electrical engineer. But I think I understand the gist of balanced audio connections… sender sends recipient a signal (positive and negative/ground conductors) plus an inverted signal (3 conductors required now). Recipient overlays the signal with the inverted signal, and anything other than silence in the result is noise that was picked up by the cable in signal transit. Recipient inverts that noise signal and overlays it on the non-inverted signal, and thus any cable noise is stripped from the signal. Easy peasy.

 

To my mind that’s three conductor per channel. For a pair of stereo headphones, that’s six conductors. So why do there appear to be two channel, single jack/plug, XLR headphone connections out there with only four conductors? I don't understand how that can be possible.

 

My DAC is a Mytek Brooklyn Bridge. The documentation clearly states that it can accept balanced connections. That is typically done with XLR connections, but it only has two 1/4" headphone connections. But they address that limitation by selling this XLR to dual 1/4" adapter. But here’s the catch. That adapter has only one XLR plug, AND it’s only got four pins. Huh? And the plot thickens…

 

I have a pair of Focal Stellia cans on order. They supply two cables. A short one (~1m) with your typical 3.5mm termination. But the other one is a long ~3m cable, a length more suitable for a balanced connection. And lo and behold, that cable is XLR terminated. But it is only one 4 pin XLR connector. With only four conductors, how can that be balanced? The same way Mytek is pulling it off? Whatever that is...

 

To complicate matters, the Balanced Headphones Guide by Headphones.com clearly states that headphones (presumably two channel) can accomplish a balanced connection with only a single 4 pin XLR connection. But contradicting that, this Focal Stellia reviewer claims that the provided 4 pin XLR cable IS NOT balanced because it only has four pins. They both can't be right.

 

And finally, a brief look at some premium headphone amplifiers clearly possess what appear to be single 4 pin XPR connections, presumably blanced. Some examples here, here, and here. Are these balanced? And if so, how?

 

Thanks for the help. 🙂

[scolley]

No replies, but found my own answer.

 

The reviewer was technically correct, but also appeared to not understand that it did not matter. The 4 pin XLR connection is not a true balanced connection, but it performs the same function. It's just not done the original 3 conductors per channel with signal processing way. Apparently this is a way that eliminates processing on either the sender or receiver's end. I don't pretend to understand it. And apparently calling it "balanced" is a bit of a misnomer, yet it still performs the same cable noise elimination function.

 

Here's a link that describes it.

 

So my takeaway is that vendors calling the 4XLR connections (as they appear to be called) "balanced" is not misleading. It's just avoiding confusion over it performing the same noise reduction function a different way. So call it balanced. Or not. You decide. In the end, the outcome is the same.

[Summit]

14 hours ago, scolley said:

No replies, but found my own answer.

 

The reviewer was technically correct, but also appeared to not understand that it did not matter. The 4 pin XLR connection is not a true balanced connection, but it performs the same function. It's just not done the original 3 conductors per channel with signal processing way. Apparently this is a way that eliminates processing on either the sender or receiver's end. I don't pretend to understand it. And apparently calling it "balanced" is a bit of a misnomer, yet it still performs the same cable noise elimination function.

 

Here's a link that describes it.

 

So my takeaway is that vendors calling the 4XLR connections (as they appear to be called) "balanced" is not misleading. It's just avoiding confusion over it performing the same noise reduction function a different way. So call it balanced. Or not. You decide. In the end, the outcome is the same.

 

The 4pin XLR connection is a true balanced connection for headphones. It is only between electrical gear that we use 2 x 3pin XLR connectors. The extra pin is for protection (safety ground) only and have noting to do with balanced transmission.  

 

Whether the amplifier works (internally) in true balanced configuration (i.e. differential signaling) or not is another matter.

 

https://robrobinette.com/Push-Pull_Vs_Single-Ended_and_Balanced_Vs_Unbalanced.htm

 

https://forum.headphones.com/t/single-ended-balanced-differential-what-it-means/3571

[scolley]

Fascinating stuff. Thanks for the clarification, and excellent links. @Summit

 

So where does the phase inversion and signal summing come into play? I've got two three pin XLR connector cables (one per channel) between my DAC and my amp, and I thought that's what was going on. Is that not correct?

 

Thanks.

[audiobomber]

This is an interesting read:

 

AUDIO MYTH - BALANCED HEADPHONE AMPLIFIERS ARE BETTER

Headphone transducers are balanced devices. They have two wires. The electrons that flow into one wire must flow out of the other. The current is always balanced. The headphone transducers cannot detect the difference between a single-ended drive and a voltage-balanced drive. The system is balanced with either type of voltage drive.

https://benchmarkmedia.com/blogs/application_notes/audio-myth-balanced-headphone-outputs-are-better

 

[yamamoto2002]

The benefit of balanced connection of headphones is 6dB louder sound can be achieved from the same amplifier power voltage. This difference is especially important for battery powered portable audio devices because power voltage is somewhat limited. Some people use very low efficiency planar headphones and want louder sound.

 

And four wires are enough for this purpose.

• Single-ended: hot - ground = applied voltage to the voice coil
• Balanced: non inverted - inverted = applied voltage to the voice coil