Introduction to sound cards

The sound card (also called an audio card) is the part of a computer which manages its audio input and ouput.

It is usually a controller which can be inserted into an ISA slot (or PCI for more recent ones), but more and more motherboards include their own sound card.

Sound card connectors

The main components of a sound card are:

• The specialised processor, called the DSP (digital signal processor), which does all the digital audio processing (echo, reverb, vibrato chorus, tremelo, 3D effects, etc.);
• The digital to analog converter, or DAC for short, which converts the computer's audio data into an analog signal for being sent to a sound system (such as speakers or an amplifier);
• The analog to digital converter, or ADC for short, which converts an analog input signal into digital data which a computer can process;
• External input/output connectors:
  • On or two standard 3.5 mm line-out jacks, normally light green in colour;
  • A line-in jack;
  • A microphone input (sometimes called Mic), usually a pink-coloured 3.5 mm jack;
  • An SPDIF digital output (Sony Philips Digital Interface, also known as S/PDIF or S-PDIF or IEC 958 or IEC 60958 since 1998). This is an output line which sends digitised audio data to a digital amplifier using a coaxial cable with RCA connectors at the ends.
  • A MIDI connector, usually gold-coloured, which is used for connecting musical instruments, and can serve as a game port for plugging in a controller (like a joystick or gamepad) which has a SUB-D 15-pin connector.
• Internal input/output connectors:
  • A CD-ROM/DVD-ROM connector, with a black socket, which is used to connect the sound card into a CD-ROM's analog audio output using a CD Audio cable;
  • Auxiliary inputs (AUX-In), with white sockets, used for connecting internal audio sources such as a TV tuner card;
  • Telephone answering device connectors (TAD), which have a green connector.