A sound card is an internal expansion card that provides input and output of audio signals to and from a computer under the control of computer programs. The term sound card is also applied to external audio interfaces used for professional audio applications.
Close-up of a sound card PCB, showing electrolytic capacitors, SMT capacitors and resistors, and a YAC512 two-channel 16-bit DAC. The integrated circuit on the left is a 3403 single power supply quad operational amplifier.
8-channel DAC Cirrus Logic CS4382 placed on Sound Blaster X-Fi Fatal1ty
A VIA Technologies Envy sound card for PC, 5.1 channel for PCI slot
Three early ISA (16-bit) PC sound cards showing the progression toward integrated chipsets
In computing, an expansion card is a printed circuit board that can be inserted into an electrical connector, or expansion slot on a computer's motherboard to add functionality to a computer system. Sometimes the design of the computer's case and motherboard involves placing most of these slots onto a separate, removable card. Typically such cards are referred to as a riser card in part because they project upward from the board and allow expansion cards to be placed above and parallel to the motherboard.
Example of a PCI digital I/O expansion card using a large square chip from PLX Technology to handle the PCI bus interface
Altair 8800b from March 1976 with an 18-slot S-100 backplane which housed both the Intel 8080 mainboard and many expansion boards
Rack of IBM Standard Modular System expansion cards in an IBM 1401 computer using a 16-pin gold plated edge connector first introduced in 1959
Configuration DIP switches in a 16-pin through-hole package as often found in ISA expansion cards from the 1980s
