Jack
A very popular connector, mainly used to connect two audio devices. It is most commonly used to connect headphones to a phone, computer, or player, but its uses are much broader than they may seem at first glance.
More about the jack connector.
The jack connector is a ubiquitous connector used to transmit analog audio signals from one device to another. Originally used primarily in manual telephone exchanges, it can now be found on almost every device that produces sound in some way—on personal computers, smartphones, or various players. Although it may be becoming less relevant due to the ongoing technological development of wireless technologies and more universal connectors (specifically USB-C), it is still a reliable connector that many people swear by.
Jack vs USB-C
Some time ago, mobile phone manufacturers switched from jack connectors to the more modern USB-C. However, this sparked a heated debate among people as to whether this was the right move or not. USB-C transmits a digital signal, while jack transmits an analog signal. A digital signal is much simpler—it consists of a signal that can mean either a one or a zero. Analog is more complex—it consists of a sine wave, and the problem with this type of signal is that it is more susceptible to interference than a digital signal. That's why, with some lower-quality products to which you connect analog headphones, you may hear a slight crackling or high-pitched tone. This is interference caused, for example, by poor insulation or grounding of the components of the product to which the headphones are connected. In this respect, digital audio has the upper hand. However, in other cases, the sound quality is virtually identical.
2.5 mm jack
The 2.5 mm jack (also known as "sub-mini") is the smallest and least used variant of the entire jack connector family. It is mainly used in older phones and headphones, or two-way radios. It was also used for power supply from an adapter.
3.5 mm jack
The 3.5 mm jack (also known as a "mini" jack) is probably the best known and most widely used type of jack connector. It can be found on virtually every personal computer, laptop, various portable players, televisions, and other devices capable of producing audio signals.
6.3 mm jack
The 6.3 mm jack is actually the first member of the jack connector family and, despite this, it remains a relevant connector that is mainly used in various professional audio devices, Hi-Fi systems, and musical instruments.
Další typy
Of course, other types have also been developed over time that have not been standardized, were created for a specific purpose, or are specified completely differently, but they work on the same principle and can be partially interchanged—for example, various types of connectors such as 5.3 mm or 6.35 mm jacks, which are used to connect microphones in aviation or various military devices.
Pins
It can be daunting to discover that professional audio equipment divides audio into "balanced" and "unbalanced," where the application and processing of connectors may differ. However, it is better to focus purely on what we encounter everywhere and thus explain the question of pins much more simply. (For the curious, we will talk about unbalanced audio.)
On the jack connector itself, you can see circles, usually in black (although there are exceptions). This marking tells you how many pins (also called "poles") the jack connector has.
1 stripe (2-pin) means that the connector only supports mono audio, specifically the left channel - suitable for hands-free headphones, where only one driver is needed. Mono headphones for both ears will produce exactly the same sound on both sides. If you plug stereo headphones into a mono connector, only the left driver will produce sound.
2 stripes (3-pin) mean that the connector supports stereo audio - i.e., left and right channels. The left and right sides can play different sounds. This type is still the most common.
Two jacks are also often paired, one for headphones and the other for microphone input. On laptops and personal computers, these jack ports are usually marked green for headphones and pink for microphone, or at least with a headphone and microphone symbol.
3 stripes (4-pin) mean that the connector can receive both stereo signal for headphones and microphone in one connector. This is found on smartphones and new laptops. However, it can also be used for video recorders and other video players.
4 stripes (5-pin) are more like jack connectors, which are only used in professional equipment.