Convert XLR to TRS Headphone Cable Issue

@052rc 

Please do as @cleeds says.

I think your second level of confusion is caused by marketing.  There is a world of difference between the claims of balanced and claims of fully balanced.

Balanced inputs and outputs can be achieved by adding extra components to accept or generate an additional inverted signal at the input and output stages of a component.  Fully balanced means that the entire signal path through the component is duplicated.  This pretty obviously increases both the cost and the ability to reject EMI.

An example, which mixes both balanced and fully balanced in one component, is my SoulNote phono stage.  This supports Moving Magnet (MM), Moving Coil (MC) and DS Audio optical cartridges.  MM signal levels are typically more than 10 times higher than MC, and DS Audio optical are more than 10 times higher again than MM. 

Most cartridges and tonearms inherently support 4-wire balanced operation, and the MC section of the stage is fully balanced (with a pair of 3-pin XLR connections for input). 

DS Audio optical cartridges need a DC power supply, so two of the wires are used for that, meaning there are insufficient signal wires for balanced operation.

The MM input uses the same balanced connectors as the MC input, but SoulNote has decided that the extra cost of fully balancing the MM input is not worthwhile. 

RCA inputs are provided, but they just hook to two of the three XLR input pins, so they cannot be used simultaneously.  Output of course is balanced via two 3-pin XLR connections.

@wncrob 

The headphone amp is model MX-HPA...it was sold as new and heavily discounted.  ... I’m beginning to think that there is an issue with the AMP. ... It’s at the selling dealer today to be analyzed ... but I doubt it can be "fixed" for XLR functionality, and a replacement is likely to have the same issues.  

I am positive there is absolutely nothing wrong with your amp, but it seems the dealer has little idea of how it should be connected to realise its sonic benefits of fully balanced operation.  Maybe this is why it was heavily discounted 

Ultimately, Musical Fidelity will have to educate the dealer.  As I posted earlier, you need to connect your headphone to both XLR outputs, one for the left channel and one for the right.  If you post your headphone make and model, we can probably work out exactly how the headphone wiring can be modified.

So, you're suggesting this manufacturer made a retail product that requires the consumer to modify their headphone cables to function properly with 3-pin XLR terminations?  I doubt it.  And remember, it works fine with a single TRS termination, but not with an adapter, TRS to 3-pin XLR.  The ONLY reason I'm having this problem is that I needed a 6-8 ft extension cable and the cable manufacturer suggested the XLR termination.  If I had a TRS termination on both ends, this thread would not exist.  

@wncrob 

this manufacturer made a retail product that requires the consumer to modify their headphone cables

On the contrary, Musical Fidelity makes high-end headphone amplifiers where the primary purpose is fully balanced operation.  For those who do not understand what this entails, and to support lesser headphones, they also provide ’normal’ headphone jacks (TRS). 

Headphone jacks with three wires cannot support balanced operation, unless two separate jacks are used.  This may be addressed in the User Manual (I have not tried to find a copy because there is an obvious solution to your issue).

"Working fine" through a single jack means the amplifier can behave like an ordinary, unbalanced amplifier, but frankly from my point of view, this is a complete waste of its real capabilities.

The ONLY reason I’m having this problem is that I needed a 6-8 ft extension cable and the cable manufacturer suggested the XLR termination.  If I had a TRS termination on both ends, this thread would not exist

Sack the cable manufacturer, if the instructions they were given were correct (I suspect they were not). 

You could buy a decent pair of headphones designed for balanced operation through two XLR connections.  Alternatively, you can easily modify the wiring of your headphones.

While you are at it, why not get a disk player with balanced output so you can really hear what your fully balanced headphone amplifier is capable of.

Or you could sell the amplifier to somebody who understands how to use it the way Musical Fidelity intends.  It runs on 240-Volts. so I’d be interested in making an offer but it has to be shipped to Australia.

Addendum:  I have now found the User Manual on-line and it clearly states that the amplifier supports two pairs of stereo headphones via 1/4" 3-connector jacks or one pair of balanced headphones through two XLR connectors.

From ChatGPT:

Balanced headphones use specialized cables (e.g., 4.4mm TRRRS, 2.5mm TRRS, or dual XLR) with separate grounds for left and right channels, eliminating common-mode noise and increasing power output. They offer improved channel separation and higher voltage for demanding headphones, requiring a balanced amplifier. 

Addicted To Audio +4

Key Aspects of Balanced Headphones

• What They Are: Unlike standard ("single-ended") headphones that share a ground wire, balanced headphones provide separate positive and negative wires for each driver.
• Benefits: Primarily, they offer higher power output (up to four times the power in some cases), which helps drive high-impedance headphones, alongside improved channel separation.
• Connection Types: Common balanced connectors include 4.4mm Pentaconn, 2.5mm TRRS, or dual 3-pin/single 4-pin XLR connectors.
• Requirement: A dedicated balanced amplifier or DAP (Digital Audio Player) is required to experience the full benefits, notes Reddit users.
• Is it Worth It? While often considered a high-end audiophile upgrade for better, cleaner sound, YouTube users note it may not be necessary if your current, non-balanced setup is already quiet and drives your headphones well. 

  Reddit +7

Difference from Balanced Interconnects
While "balanced" in pro-audio refers to noise-canceling cables between equipment, "balanced headphones" simply ensure that the left and right driver signals remain separated from the amplifier to the headphone drivers, which can reduce distortion

Richard, I stand corrected...you are EXACTLY  right.  Many thanks!

My CD player (Ayre) has 1 set of balanced outs, but I use them for my main system & speakers, and, frankly, with the headphones, I think I'll be happy with the TRS terminated cable.  My headphones, Grado GS3000x, are hard-wired, so modifying the cabling is more than I am willing to undertake.

Again, thaanks for the education and patience!

WNCRob