Convert XLR to TRS Headphone Cable Issue

cleeds

It never ceases to amaze me how when someone doesn't understand something they resort to insults. All you had to do was ask me to clarify my post. The silly thing is you don't have to take my word for any of it. Simply look at the schematics for any so called "balanced" headphone amp and see for yourself. If you had trouble reading it, I would have explained. 

I made 2 main points in my post. The first is most people fall for the balanced headphone scam. You clearly fell for it. The second was the technical reasons to back it up. I'm not changing a word of my post because every word of it is correct. You fell for the advertising. Instead, get the schematics for this MF headphone amp, or any other one that claims to be balanced, and then we'll see who knows what they're talking about. But I know this will never happen. Once you see how it works, You'll have to admit you were wrong. I've confronted several manufacturers on this and everyone of them reluctantly admitted that I was right.  

hertzhead,

I know you have been getting some conflicting information on all of this, so I'll try to clarify it for you. Cleeds went out of his way to throw insults, but not you so I'll try to help. The information in my post is correct. If you read my 2nd post to cleeds, I show you how to fact check me so you don't have to take my, or anyone else's word for it. When MF makes the claim that you amp is fully balanced from input to output, they mean it in the same way a regular, full size integrated amp would have it. Its the same thing. Its a preamp and a power amp in one box. The only difference is the power amp section is much smaller because headphones don't need as much power. In general, there's 2 ways a component can be balanced. One way is to convert the signal from single ended to balanced at the inputs and outputs. With this method, the signal is only balanced when its going through the cables. Its very cost effective to go this route. It helps with noise and it lets you run longer cables. A fully balanced component is when double up on everything in the signal path, and keep the signal balanced as its going through the component itself. For your situation, and what we are talking about here, it doesn't matter which way its done. When MF is claiming to be fully balanced from input to end, they mean fully balanced at signal level. Everything in the preamp will be fully balanced but only the input section of the power amp will be balanced, not all the way to the speaker/headphone outputs. And this is no different for any fully balanced power amp, full size or headphone. As I stated in my first post, manufacturers are reluctant to admit that they are bridging the power amp. They label the output balanced because the signal needed to be balanced to bridge the amp. And yes, you are going from a 3 conductor headphone cable to a 4 conductor headphone cable. When most people see that, they just assume its balanced. Fully balanced power amps and single ended power amps, both use 2 conductor speaker cables. It makes no difference. 

What I'm telling you in my posts is not well known. Pretty much every person who reads them will say I'm wrong. I can't help that and I know it makes things confusing for you. If you can get the schematics for your headphone amp, or another "balanced" headphone amp, I can walk you through it and prove what I'm saying is true. But that's the best I can do. If it makes any difference, I've confronted several manufacturers on this, and every one of them reluctantly admitted I was right.    

@052rc 

I’ve confronted several manufacturers on this, and every one of them reluctantly admitted I was right

I am 100% with @cleeds on this one, unless you can get Musical Fidelity to agree with you .in writing.

Here is the confusion.  The headphone amplifier outputs a fully balanced signal for headphones, using two 3-pin XLR connectors, one for each channel. Each channel uses two wires to carry the balanced signal, for a total of four active wires, probably in two separate cables.

Unfortunately, as a bit of a gimmick, it also allows a standard headphone jack to be inserted into the middle of either of the XLR connectors. I presume this is a three-section jack designed to carry a non-balanced stereo signal over three wires (left, right and common).  So when the OP plugs his jack in, he gets unbalanced stereo.  My educated guess is that it does not matter which side he uses (left channel may become right, who knows)!

To get the undoubted benefits of truly balanced operation, he needs to rewire each side of his headphones directly to its own 3-pin XLR connector and completely remove any jack.

It is London to a brick that when Musical Fidelity says one of its products is fully balanced, its active circuitry is doubled from input to output. 

Ideally the attached player should output in balanced mode too.  Then the signal path from the output of the player to the coils of the headphone will be fully balanced.

Note:  balanced means the signal is duplicated on two paths, where one path is the opposite polarity of the other.  The combined signal is twice the magnitude of an unbalanced signal.  More importantly, Electro-Magnetic Interference (EMI) acts equally and oppositely on each path, and is cancelled out in the combined signal.

Balanced circuitry, explained clearly and concisely by Uncle Paul: 

https://www.psaudio.com/blogs/pauls-posts/true-balanced

There's a half dozen consecutive posts on the subject.

052rc

I made 2 main points in my post. The first is most people fall for the balanced headphone scam. You clearly fell for it. The second was the technical reasons to back it up. I’m not changing a word of my post because every word of it is correct. You fell for the advertising. Instead, get the schematics for this MF headphone amp, or any other one that claims to be balanced, and then we’ll see who knows what they’re talking about. But I know this will never happen. Once you see how it works, You’ll have to admit you were wrong. I’ve confronted several manufacturers on this and everyone of them reluctantly admitted that I was right.  

That is most remarkable! You have a very special way of assessing how balanced lines work and how effective that can be. Good for you! That you have convinced "several manufacturers" of your views is especially impressive.

I’ve long considered Bill Whitlock to be a particular authority on this topic. As an expert, I’m sure you’ve seen his AES paper "Balanced Lines In Audio Systems: Fact, Fiction, and Transformers," which is free to AES members here. It’s peer reviewed and as an AES member I’m sure they’d welcome your comments. If you’ve let your AES membership lapse, you might be able to find a copy of the paper at academia.edu. (You may need to sign up for an account.) 

Another excellent treatment by Whitlock is "Design of High-Performance Balanced Audio Interfaces." Also peer reviewed, published by AES and open for comments. A free copy is here, at least for the moment.  

Given your insistence that balanced audio is: 

... a marketing gimmick. There is no such thing. The people that make this stuff use the term balanced, put xlr connectors on the gear and hope you don’t ask too many questions ...

... I’m sure the professionals would welcome your thoughts. Perhaps they will be more accommodating than me. For those who might miss your AES comments, please also report back here. Have a Great Day @052rc.