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November 29, 2011

A Balanced to Single-Ended Heaphone Adapter Cable

Balanced circuits have been around for quite some time, but the first commercially available balanced drive headphone amp was created by Headroom nearly ten years ago. Balanced drive doubles the slew rate and voltage swing available from a circuit and reduces distortion. For balanced headphones, it also eliminates the ground connection between the left and right drivers, preventing crosstalk. There are many headphone amp manufacturers producing balanced headphone amplifiers now, including Ray Samuels, Eddie Current and Bottlehead just to name a few.

There isn't an "official" balanced headphone connector, but there are two methods that seem to be the most common; a dual-three pin XLR where only two of the three pins on each connector are used, and a four pin XLR where all four pins are used. Headroom, being the first to market with their balanced headphone amplifier, went with a dual-three pin XLR. Many manufacturers offer both options. I'm personally of the opinion that a 4 pin XLR should be used; it's a cleaner, easier cable to produce and a lot less heavy if using a balanced to single-ended adapter. 

The Eddie Current Balancing Act Features both 3 and 4 pin connections

Headphones, in order to be balanced, require a complete recable or a retermination if the left and right ground are isolated from one another. Balanced to single-ended adapters are used when someone has had their headphone recabled or terminated to a balanced connection but wants to listen to a single-ended headphone amplifier. In the case of the 4 pin, it's a 4 pin XLR connector to a TRS cable. This cable connects the two grounds to the Sleeve, the "S" of the TRS (TRS stands for Tip, Ring Sleeve). 

In this post, I will be creating a 4 pin XLR connector to a TRS cable using a 4 pin gold Neutrik XLR jack, a Furutech TRS (FP-704 G) and some Cardas litz wire in Teflon. It doesn't appear that there are any boutique 4 pin XLRs at the time of this writing, but the Neutrik 4 pin should not be discounted, it is very well made and solid.

My adapter cables are typically one foot in length, they can be less, but the connectors themselves are large and there should be appropriate space between them so the cable has plenty of room to bend. The process is started by trimming four identical lengths of wire. Cardas litz wire is a number of different gauges of wire, each covered in enamel that needs to be melted away with hot solder (a solder pot is especially helpful). Each length of wire is stripped at the end, the enamel melted away, and soldered to the solder tabs on the 4 pin XLR. One can cover the solder tabs with heatshrink to be extra anal ;)

The wire is then braided into a litz configuration in preparation for sleeving. 

3/8" Black Nylon multifilament sleeving is trimmed with a hot knife and slipped over the braided wire. Two pieces of heatshrink holds the nylon sleeving in place, and the strain relief grip is placed under the 4 pin connector. 

The metal sleeve is slipped on top of the 4 pin connector and the plastic strain relief grip is covered by the bottom piece which screws in place, creating a strong grip on the heatshrink and nylon sleeving. 

A logo'd piece of heatshrink is added underneath the existing piece so it will be exposed under the Furutech connector. The other side of the wires are stripped and tinned with solder. 

The Furutech TRS is dissasembled in preparation to be attached to the cable, you'll see the four pieces below.

The wire is now soldered in place. The typical wiring configuration for a 4 pin XLR is as follows:

Pin 1 - L+
Pin 2 - L-
Pin 3 - R+
Pin 4 - R-

Therefore pin 2 and 4 are connected to the sleeve of the Furutech, pin 1 the tip (left channel), and pin 3 the ring (right channel). The plastic strain relief grip is set in place under the TRS and the metal top and bottom are slipped in place.

The metal top portion of the connector compresses the strain relief grip, the bottom metal portion can now be screwed in place. 

The cable is now complete and is checked with a multimeter for continuity and resistance. 

I hope you enjoyed this step-by-step process of building a balanced to single-ended heaphone adapter cable. Zynsonix can build you one just like it or one built to your specifications.

The Fine Print:
The above steps detailing the building of a cable are for entertainment purposes only, and not to be performed under any circumstances. The owner of this blog and all associated parties can not / will not be held responsible if you attempt the process posted and cause physical harm to yourself, your surroundings or your property. Please keep this in mind.


  1. isn't really sad that a person can publish such excellent information, on a technical blog BUT then feels compelled to include a disclaimer so some nut won't sue them?

  2. Excellent work, but why not use an adapter like proel AT295

  3. Thanks! The Proel is 3 pin, versus the 4 pin we need. Also this solution puts less stress on the jack. 3.5mm mini and 6.25mm TRS jacks are known to get a scratchy connection (or full channel dropout) over time if there's pressure pushing the little internal pins away from where they should be.