The Pi Model B+, Pi 2 and Pi 3 features a 4-pole 3.5mm audio jack which also includes the composite video signal. This has allowed for the removal of the composite video socket found on the original Model B.
The new jack is a 4-pole socket which carries both audio and video signals. It’s similar to sockets found on other multimedia devices such as iPods, MP3 players and smartphones. It now used on the A+, B+, Pi 2 and Pi 3.
4-pole Audio Jack
This style of connector is sometimes referred to as “TRRS“, which stands for “Tip-Ring-Ring-Sleeve”.
The four conductors carry video, left audio, right audio and ground. Cables are easy to obtain but use different configurations so you must be sure how your cable is wired before attempting to use it with the Pi.
Here is a table showing the configuration of various popular devices :
|Device||Sleeve||Ring 2||Ring 1||Tip||OK?|
3.5mm Audio Jack Cable Availability
Cables are readily available but they don’t all follow the same standard so you need to be careful before assuming it will work with your Pi. The good news is that many will still work but you may need to swap the video cable for one of the audio channels.
Cables should be avoided where the ground connection appears on any ring other than Ring 2.
As you can see from the table all the cables where the ground in on Ring 2 will work with the Pi although the camcorder style will require you swap your Video with the Right Audio plug.
Traditionally composite video uses the yellow coloured sockets whereas audio uses the Red (Right channel) and White (Left channel). Cables are available with both RCA plugs or RCA sockets on the end. Make sure you buy a cable with the appropriate connectors for your video and audio accessories.
Multimeter Continuity Check
If you’ve got a multimeter you can check where the ground is on your cable. Check the continuity between the rings on the cable’s 3.5mm plug and the outer metal shell on the coloured RCA plugs.
If the shells are connected to “Ring 2” as shown above your cable should be OK.
Finally if the ground appears on “Ring 4” the cable should not be used with the Pi’s audio jack.