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Why don't balanced headphones use 4-pin or mini 4-pin XLR?

post #1 of 12
9/8/07 at 2:59pm
Thread Starter 
I understand balanced headphones use dual 3-pin XLR plugs, however I don't understand why. The third pin in the XLR plugs, which afaik would be used as ground on speakers, is not used for anything on balanced headphones. So when you total up how many pins are being used, it is 4, two in each plug.

Which leads me to my question. Why don't balanced headphones use a single 4-pin or mini 4-pin XLR connector? It would seem to me that it would be a LOT more convenient, and adapters to single ended would also be a lot more convenient. Why is it not done like this?

Also, do balanced interconnects work the same way? With only 2 of the 3 pins being used per single cable? If so, then balanced interconnect cables could be reduced to a single 4-pin XLR m-m cable! Why would it not be done like this? It just seems counter intuitive to me. Unless there is some other reason which I missed.
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post #2 of 12
9/8/07 at 3:09pm
Some answers here, a thread started not long ago.

http://www.head-fi.org/forums/showthread.php?t=259093
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post #3 of 12
9/8/07 at 3:14pm
Pin 1 (the "third" pin you refer to) is for the cable shield, which can also be optionally left out in line level interconnects (if you ever see a ground lift switch by an XLR jack, that's what it does). Now if you were using the cable for something like a phantom powered microphone, you'd absolutely need all three, but that's another story.

I think the real reason why two 3-pin XLRs are used is just the inertia from Headroom having originally done it that way on their balanced amps. There is no technical reason with headphones that necessitates using the 3-pin XLRs, and many people indeed do use 4-pin XLRs and add a 4-pin jack to their amp. If you think about it, AKG used a 4-pin XLR on the K1000, and we both know how adept they are with headphones.
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post #4 of 12
9/8/07 at 3:26pm
Thread Starter 
Reading through the thread luidge posted confirms what I was thinking. There is no real reason to use dual 3-pin.

Also in that thread was how using dual 3-pin became the norm:
Quote:
Originally Posted by Hirsch View Post
The main reason that Headroom launched their original balanced amp with a pair of 3-pin connectors is that the original Blockhead was essentially two Maxes strapped together. So, with one Max driving each channel, the headphone output on that amp could only support one channel in balanced mode. A 4-pin connector was simply not an option, with each channel in a different chassis.
Also the idea that the third pin is used for ground (even though it almost never is on the actual headphone cable) can also be shot down:
Quote:
Originally Posted by grawk View Post
You can wire the shield to the shell on the connector. Most balanced cables the shield is only connected at one end anyway.
And what's more I have a great idea that would allow the use of a single interconnect between components in a fully balanced setup. Use a 5-pin XLR cable, and wire the left ground to the 5th pin and the right ground to the shell of the plug.

Manufacturers should start doing things this way!

Quote:
Originally Posted by Fitz View Post
If you think about it, AKG used a 4-pin XLR on the K1000, and we both know how adept they are with headphones.
Yes and there's that too!
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post #5 of 12
9/8/07 at 5:30pm
I have asked the same question before and it boils down to: "Well that is the way we have been doing it forever". I say it is time to change and make things both cleaner and cheaper.
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post #6 of 12
9/8/07 at 6:06pm
There is no real reason so....I converted the two TRS balanced plugs to 4pin XLR. It doesn't sound any different but it's more convenient to use one plug than 2 plugs.
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post #7 of 12
9/8/07 at 6:28pm
Quote:
Originally Posted by 003 View Post
Why don't balanced headphones use 4-pin or mini 4-pin XLR?
Because amplifiers with balanced outputs use dual 3-pin XLR connectors...
Using the corresponding XLR plugs on the headphones makes sense, since you then don't need to use a converter cable.
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post #8 of 12
9/8/07 at 8:31pm
Quote:
Originally Posted by 003 View Post
And what's more I have a great idea that would allow the use of a single interconnect between components in a fully balanced setup. Use a 5-pin XLR cable, and wire the left ground to the 5th pin and the right ground to the shell of the plug.

Manufacturers should start doing things this way!



Yes and there's that too!
In the pro audio world, frequently, 7pin xlr is used for 2 channels of fully balanced audio. 5-pin works well for shorter runs, and for headphones, the 4 pin standard has been around longer than dual 3 pin (k1000, k340).
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post #9 of 12
9/29/07 at 6:41am
You know, I was wondering this too.

I am going to recable my Sextetts to 4-pin balanced...And then when I have enough scratch to get a balanced amp and source, DIY/modded/custom amp, DIY/modded/custom source.

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post #10 of 12
3/8/11 at 7:36pm

Bumpity-bump,

 

If anyone is still subscribed to this thread maybe you can provide an answer to this:

 

I believe that for a balanced headphone cable, when using shield wires they would be connected to the unused pins of dual 3-pin xlr connectors, and go unconnected to anything at the headphone end(?). But what about when using a single 4-pin xlr instead of the dual 3-pins, would you connect the shield wires just to each other at the xlr end, or just leave them unconnected to anything like on the other end?

 

I understand that many feel that shield wires aren't even necessary for this type of cable but that is not what I am trying to figure out.

 

Thanks blink.gif


Edited by grokit - 3/8/11 at 8:00pm
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post #11 of 12
3/8/11 at 10:06pm

On all my 4 pin Amphenol XLR connectors, male and female, chassis mount or not, there is a different looking fifth tab to solder the shield, which eventually ties to ground if the amplifier is correctly grounded at the chassis.  3 pin XLR for headphone usage is plain silly.

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post #12 of 12
3/10/11 at 2:47am

Thanks Sam, agreed. There is a certain cable maker that we all know can't solder but I had a feeling his design was screwey as well, and you are not the only one to confirm this. Four shield wires, connected to nothing at all, not even each to other does nothing but make a cable twice as heavy lol.

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