Build a replacement cable for the Etymotic ER-4P

Bulding a replacement cable for the ER-4P

What you need:

  • A piece of perfboard with regular 0.1" spacing
  • A headphone cable (preferably a good one). You can simply cut the phones off a cheap headphone, and you have the cable.
  • Heatshrink tubing in different sizes
  • A heat gun to shrink the heatshrink
  • some 1.2 mm2 diameter copper wire
  • some 1 mm2 diameter copper wire
  • several 22 Ω resistors
  • A file or rotary tool (e.g. a Dremel)
  • A multimeter

How you'll do it

First, make the pins for the new headphone cable. To do that, clip off two shortish length from the copper wire, remove the coating (if applicable). Then, use the file on the 1 mm2 wire to remove the sharp edges and round off the tip a bit. Do the same with the larger wire.

However, the larger wire won't fit into the perfboard holes as is. Use the file to make the wire thinner at the end you did not file round until it fits into the perfboard (a rotary tool helps here). Now, solder the two pins into two unconnected perfboard holes pointing out towards the non-metal side. These are the pins that will plug into the drivers' holes later.

Use the multimeter to select the two resistors that are closest to each other in their resistance (you don't want to have your right headphone louder than the left, do you?). Then, solder one to the fat pin on the backside of the perfboard (where the metal is).

Almost done! Now put a thin heathrink on the headphone cable and slide it back. Use the multimeter to test which pin goes to which part of the stereo plug on the original cable, and solder the headphone cables to the pins accordingly (I think the sleeve was the fat pin, but I'm not sure).

Cut out the piece of perfboard as small as possible. Then, slide a larger piece of heatshrink over the plugs. Press the heatshrink on the pins, and cut two holes into the heatshrink. Then, shrink the heatshrink with the hot air gun. Add some hot glue to fasten the cable (if needed).

Note you need to do this twice: Once for the left and once for the right driver.

Author: Jan Seeger