Preparation

This is how I converted my Beyerdynamic DT 770 Headphones from having a fixed cable to having an aux jack.

The first thing I did was remove the left driver (Or, the side with the cable going in).
Then I de-soldered all of the cables connected to the driver, and removed the original cable from the earcup.

The pins are, from left to right, Left, Right, and Ground. There is no reason to open the right ear cup (The side without the cable).

Try not to pull or exert force on the driver pins ever. The left-most and right-most pins are connected directly to the **extremley** fragile voice coil, so pulling the pin out will break your driver. And then you won't be able to fix it. And the drivers are expensive to replace.

I used a 3.5mm jack from radioshack. In hindsight, I would recommend finding a higher quality, sturdier part.

I also needed 3 extra wires to connect the new 3.5mm jack to the driver (left, right, ground), and this 3-pin fan cable from an old Bitfenix computer fan seemed perfect. I cut out a segment around 1-2 inches long to use. RIP fan.

Attach Connector to Drivers

I then soldered the 3 wires to the connector. I had it plugged in and playing a left/right channel test sound so I could then ensure that I connected the correct wires on the other side to the driver.

I soldered the left and ground wires from the connector to the driver (first & last pin, respectively. In the below image, the right side is not attached yet.

Note: The right channel wires doesn't actually need to be attached to the middle pin on the left driver. You can just connect the 3.5mm jack directly to the right channel wire and it would work the same.

The right side + and - are in the cable coming in from the top of the left ear cup. The white one is positive and the non-sleeved one is ground. I soldered the right + wire and the right wire from the jack to the middle pin of the left driver, although as I noted above, it is not necessary.

I also soldered the right ground to the right-most pin on the left driver, where the connector’s ground is also attached.

The right side wires would occasionally short with the ground wire near the pin, which would cause the sound on the right to drop out randomly. I had wrap a small piece of electrical tape around the ground wires to prevent this.

The work with the driver was done so after testing that is was working correctly, I re-assembled the driver with all the various things that were there before.

The cable hold on the earcup was too small for the 3.5mm jack to fit through, so I enlarged it slightly. By melting it away with my soldering iron. That was not best-practice but it worked…


Wire hole from the outside, post-enlargement.

I aligned the 3.5mm jack with the hole and affixed it with a hot-glue gun. This particular jack came with a nut that threads on to it from the outside, which helps hold it in place more than the glue. You can see it in the second-to-last picture.

The Cable

At this point I completely re-assembled the headphone, as the modification was complete. I was also left with the original cable, which now had a plug on one end and was just cut on the other end (as it was previouslty connected to the headphone).

You could use any aux cable with the headphones at this point.

I got a 3.5mm plug from RadioShack to “convert” the old cable into a normal aux cable. The three wires in the cable were coated in colored insulation that I had to burn away with a lighter before connecting them to the new plug.

The plug I used here made the wire poke my should while wearing the headphones because it was too big. I later swapped it out for a smaller REAN connector.

Result

Here is the final result of this modification.

With the cable plugged in.