If you've ever looked at the stereo plug on your headphones or your guitar cable and wondered why some plugs had two rings and some had three, you're not alone. Both types of plug have a different use, and each ring on those plugs serve a different purpose in the function of the cable. Pulling apart the plug reveals a jumble of metal pieces and colored wire attached to each other. The function of each piece is simple to understand once you know what each one is doing.
The three ring adapter is also known as a TRS (tip-ring-sleeve) adapter. The two ring adapter is known as a TS (tip-sleeve) adapter. The two ring adapter may also be called a "phono plug." Each adapter is available in 2.5mm, 3.5mm, 1/8 and 1/4 inch sizes. Adapters are also available in an RCA type plug.
Three ring and two ring adapter cables can have a combination of any number of plug types on the opposite end of the cable. For example, one end may have a 1/8-inch plug while the other has an RCA plug.
A two ring adapter is made up of three main parts: the tip, the sleeve and the housing. The metal "tip" portion of the adapter carries the main audio electric pulses from the sound producing device, through the adapter to the output. The metal "sleeve" portion acts as an electric ground to avoid short circuits in the electronic devices.
The three ring adapter contains four main parts: the tip, the ring, the sleeve and the housing. Like the two ring adapter, the sleeve portion acts as a ground to avoid electric short circuits. However, the other parts of the adapter act differently. Stereo audio relies on both a left and a right audio channel to create separation. The tip portion acts as the left channel, while the ring portion acts as the right channel.
Balanced vs. Unbalanced
"Balance" refers to the impedance of an audio signal when compared to the ground connection. If there is only one signal conductor and the ground, as in the TS connector, the connection is unbalanced. If there are two signal conductors and a ground, as in the TRS connector, the impedance is balanced between the two signal conductors, and so the connector is "balanced."
The two ring adapter functions as an unbalanced sound device connection. Similarly, the three ring adapter functions as a balanced sound device connection. In professional audio situations, both of these adapters function as monaural (mono) audio signals. TRS or three-ring adapters, however, can be used as unbalanced stereo adapters on headphones.
The plugs are generally used in audio applications such as instrument amplifiers, microphones or audio mixing boards. Two- and three-ring adapters may also be found in video production equipment, though usually for the purpose of transmitting sound to the video recording devices.
TRS and TS cables and adapters are used in a variety of audio applications. These include, but are not limited to amplifiers; microphones; video camecorders; sound recorders; stereo receivers; DVD players; CD players; computers; audio mixing consoles and portable audio players.