Mono vs Stereo Signal
Mono and stereo basically differ on the number of channels used to send signals to speakers. Mono uses only one channel and the sound can be reproduced on several speakers. On the other hand, stereo uses two different channels resulting in more details and more realistic audio than mono. Because it has better sound quality overall, a vast majority of audio systems today support stereo; however, mono signals are still used where stereo fails because of phase cancellation.
Balanced vs Unbalanced Audio
The signals carried by audio cables can either be balanced or unbalanced. An unbalanced cable has two wires; one wire carries the signal while the other serves as the ground which shields the signal wire from noise. However, the ground wire also serves as an antenna which means it can pick-up noise as the signal travels from the source to the destination. Because of this, unbalanced signals are suitable for shorter cables to minimize, if not completely remove, unwanted noises.
On the contrary, balanced cables have three wires; one for the positive signal, another one for the negative signal, and a third wire for the ground which works the same way as with the balanced cable, only in this case, it shields two rather than just one cable. The positive and negative signals are exactly the same but have opposite polarities which means they cancel each other out as they travel from the source to the destination. The ground wire still picks up noises along the way but the magic happens at the receiving end. Once the signal reaches the destination, the negative signal’s polarity is flipped so it becomes in-sync with the positive signal and puts back the original audio signal from the source. What happens to the noise? Unlike the audio signal, the noise signals do not have a reverse polarity after being picked up by the ground wire. Once it reaches the receiving end, the signal is also flipped, causing the positive and negative to cancel each other out, eliminating the noise signal. This is also known as the Common Mode Rejection technique. Balanced cables thus have neater, clearer output and can be used over longer distances than unbalanced cables.
TRS cables have three contact points, the Tip, Ring, and Sleeve. TRS can either carry mono, balanced audio or stereo, unbalanced audio. There are three varieties of TRS cables: ¼-inch, 3.5mm, and 2.5mm. ¼-inch cables are most often used for balanced signals, using the Tip and the Ring to carry the audio signals and the Sleeve as the ground. The 3.5mm variety on the other hand are mostly used to carry stereo, unbalanced signals using the Tip and the Ring as channels for the left and right speakers and the Sleeve as the ground. The Common Mode Rejection technique is not applied on 3.5mm cables since the two contact points are used as channels to deliver audio to left and right speakers, earpieces, or cups of audio devices thus, it can only send out unbalanced signals. The 2.5mm type is used on mini-jack connectors normally found in older phones and TTY devices.
The TRRS cable is a TRS cable with an extra Ring on it. The additional contact point usually serves as the channel for microphones. The audio jack on most laptops, smartphones, and game consoles are TRRS jacks allowing you to listen and speak using the built-in microphone of the TRRS headset or earphones. Some AV cables for camcorders also use TRRS where the additional contact carries video signals. Like TRS, TRRS cables come in ¼-inch, 3.5mm, and 2.5mm sizes but ¼-inch TRRS are not as common as the 3.5mm variety.
Majority of TRRS cables follow the American Headset Jack AHJ/CTIA standard where the Tip and the first Ring carry the left and right channels, the second Ring as the ground, and the Sleeve as the microphone or video channel. The less popular standard used by TRRS cables is the OMTP standard where the second Ring is used for microphones and the sleeve as the ground.
TRRS cables typically carry stereo, unbalanced signals since the additional contact point is not used to balance out the signals but to carry microphone or video signals instead. However, some devices would make use of the additional conductor to carry balanced signals.
TRS and TRRS Compatibility
In general, TRS headsets or earphones can work with the TRRS socket of smartphones, tablets and computers. Once it’s plugged in, the internal speakers of the device are automatically shut off but the device’s mic remains active. Similarly, a TRRS headset can be plugged into the TRS port but you will only be able to use it for audio output, while the mic’s channel is kept inactive.
As for TRS microphones, since it is designed for audio input rather than output, the wiring is different and is therefore not directly compatible with the TRRS socket. A TRS to TRRS adapter would be necessary for it to work.
Digital microphones are also available for recording and these use digital connectors like Lightning or USB-C. If you are recording using a digital mic, make sure that you don’t plug-in a TRRS headset. In most cases, the built-in mic of the TRRS headset will override the digital mic. Use a TRS headset instead.
Which is better?
TRRS may have an additional contact point for an additional channel but does not necessarily make it better than TRS. Each cable serves its purpose in ways similar or different from the other but they co-exist because one may be used where the other is not suitable.