Make a 3.5mm Headphone Splitter (Video Tutorial Project)

By · Founder, DIYTech Labs

A headphone splitter lets two people listen to one phone or laptop — perfect for watching a film together on a train or flight. They are cheap to buy, but building one teaches you how audio jacks are wired, and you can make it exactly the length you want.

Parts and Tools

  • One 3.5mm male stereo (TRS) plug
  • Two 3.5mm female stereo sockets
  • A short length of 3-core or shielded audio cable
  • Soldering iron, solder, wire stripper, heat-shrink tubing

How the Wiring Works

A stereo jack has three connections: Tip = left channel, Ring = right channel, Sleeve = ground. A splitter simply connects all three, in parallel, from the plug to both sockets: tip to both tips, ring to both rings, sleeve to both sleeves.

Steps

  1. Prepare the cable ends and slide heat-shrink on before soldering.
  2. Solder the three wires to the male plug: left, right, ground.
  3. Split the other end and solder the same three connections to each female socket.
  4. Insulate every joint with heat-shrink, close the housings, and test with two headphones.

Troubleshooting

Built it and something sounds wrong? In roughly the order you are likely to meet them:

  • Only one side (left or right) plays. Almost always the ring connection: either the right-channel wire is not soldered to the ring contact on one of the sockets, or the plug is a mono (TS) plug instead of stereo (TRS). Check that every plug and socket has three contacts, then re-flow the ring joints.
  • Sound in one headphone only, fine in the other. The wiring is probably right and one socket's joints are not. Swap the two headphones around: if the silent side follows the socket, re-solder that socket; if it follows the headphone, the headphone's own cable is the problem.
  • Buzzing or humming. A ground problem. The sleeve (ground) connection is loose, cold-soldered, or the cable shield is touching a channel wire. Remake the ground joints, keep the three conductors separated, and make sure no stray strand bridges two contacts.
  • Everything sounds thin or "karaoke-like". The left and right channels are shorted together, or ground is connected to a channel by mistake. Compare your wiring against the tip/ring/sleeve diagram above, contact by contact.
  • Crackling when the cable moves. A joint is mechanically weak. Support the cable with the housing's strain relief, and let heat-shrink hold the joints so movement does not flex the solder itself.

The original video walkthrough was published on the DIY Tech Pro YouTube channel. More from us: DIYTech Labs and our Android apps.