How to Wire a Jack Plug or Audio Phone Jack Plug

Identify Connections and Solder this Common Connector Correctly

Mar 30, 2009

The jack plug (phone jack in US parlance) is a very common audio connector, but is wired in several different ways. Identify the differences to get a good connection.

The audio jack is a family of connectors, which are often used in several different ways. They are wired differently depending on the usage, but first it is important to identify the connector to hand.

1/4 inch Jack Plugs

The 1/4 inch jack plug is commonly used on musical instruments and used to be common for headphones on hi-fi equipment. Jacks are either 3-pole, where there are three metallic contacts insulated from each other by two non-conducting rings, or two-pole, with two contact surfaces insulated by one non-conducting ring. The two-pole variant is common for musical instruments like guitars, carrying a mono signal and earth. The signal is invariably on the tip of the plug, and the metallic sleeve closest to the body of the plug is the shield/ground.

Three-pole jack plugs either carry an unbalanced stereo signal, or a balanced mono signal and ground.There is a subtle variation in the tip-ring-sleeve (TRS) jack plugs used in professional audio installations for balanced audio, and the common stereo jack. The professional TRS jack can be told apart by the fact that the tip and ring metal parts have a smaller diameter than the sleeve, and TRS plugs often have brass contact surfaces. Stereo jacks are usually nickel-plated, so there is a colour difference too. Forcing the domestic stereo jack plug into a professional TRS socket will often bend the contacts of the socket so it does not make good contact in future when mated with a TRS plug.

3.5mm Stereo Jack Plug

The 1/4 inch jack is far too big for portable audio devices, so jacks are made in 3.5mm diameter. This is the ubiquitous stereo headphone plug, as used in iPods, computer sound cards and portable audio gear. The allocation of tip-ring-sleeve follows the same lines as the 1/4 inch jack.

These are often also used for unbalanced microphone inputs for small solid-state recorders. Unfortunately, although stereo 3.5mm jacks are used for the mono microphone inputs on computer sound cards these are wired differently, so computer microphones do not usually work with standard audio recorders.

Mono Jack wiring

Stereo Jack Connections

Balanced Audio Tip-Ring-Sleeve (TRS) Jack Plug Connections

PC99 computer Audio connections (3.5mm 3 pole jack)

As used on PC sound card microphone inputs (outputs and line inputs follow the regular stereo jack connections above). 3.5mm connectors are used.

TRS Insert jack

It is worth consulting the mixer manual for this, since some equipment places the send signal on the tip but the opposite, ring send may occasionally be found.

The jack plug is a versatile connector which has been used for audio since the early days of the 20th century (it originated in telephony usage). Fortunately the stereo configuration is the same across the 1/4 inch and 3.5mm types, which is probably the jack connector most people come across as the headphone plugs of their portable music players.

For portable applications, using the right-angle version of the jack can reduce the strain on the equipment sockets; the socket is often mounted on the internal printed circuit board without strain relief to the equipment case for cheapness, so the socket is often a weak point.

The copyright of the article How to Wire a Jack Plug or Audio Phone Jack Plug in Analog & Digital Audio is owned by Richard Mudhar. Permission to republish How to Wire a Jack Plug or Audio Phone Jack Plug in print or online must be granted by the author in writing.