What Is an Audio Port on a Computer?by Timothy Smithee
An audio port on a computer is any receptacle or jack to which an audio device such as speakers, headphones or a microphone can be connected. All laptops and some desktops have built-in speakers, but for better sound or privacy, you will need to connect external audio through one of the ports.
There are many possible sources of sound on a computer, including music CDs, online videos and games. Regardless of the source, all sounds start as digital audio – numbers in a file. Between the source file and the speaker, the audio must be converted to an analog format. Microphones capture an analog audio signal, which is converted to digital. The conversions happen inside or outside the computer, depending on the port type.
Analog Audio Ports
The oldest and most common port is the analog, 1/8-inch round jack used for headphones and speakers. The signal is not strong enough to drive most speakers, so computer speakers usually include a small built-in amplifier with its own power supply. The port is often identified by a green ring around the jack; a jack with a pink ring is for connecting an analog microphone.
USB Audio Ports
The USB connectors found on all present-day computers can be used as audio ports. Some external speakers and headphones, particularly headsets consisting of headphones and microphone, connect to a USB jack. The audio signal carried by USB is digital, so it may be a higher quality source of audio, but it will need to be converted to or from analog by the external device, which will affect sound quality.
Digital Audio Ports
The best possible audio quality from a computer is obtained by using a SPDIF (Sony/Philips Digital Interconnect Format) port. This is a digital audio output, and it can be either an RCA jack or an optical jack. The former can be used with any RCA cord, while the latter requires a fiber optic cable. These ports are not widely available but can be added using an external USB device. The SPDIF port is used to send audio signals to an external sound or home theater system.
Additional Analog Ports
Some computers have analog ports to plug in more speakers for surround sound. These may include rear (black), side (silver) and center or subwoofer (orange). A blue 1/8-inch receptacle usually denotes a line level input, which can be used to record sound from an external audio system. A sound card can be used to add additional audio ports to a computer.
Some laptops have a single 1/8-inch audio receptacle. These computers use software to determine whether headphones, a microphone or a headset has been connected. Analog and digital devices are not interchangeable. There are no adapters that allow connecting a USB headset to a 1/8-inch audio jack, and changing the plug will not work. Similarly, although the RCA SPDIF connector will fit the line input of any stereo system, it will not work. It must be connected to a digital input.