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Sound Card

Sound card (audio card, audio interface) is computer sound module for input/output of audio signal (in analog or digital format).

Read below short and informative articles about PCI, PCIe, USB, FireWire cards, about analog and digital connectors.

Sound cards

Audio card convert:

1) an analog signal at linear input to digital signal coming to computer.
2) a digital signal stored or created into computer to analog for listening at loudspeakers or headphones.


- for playback multimedia audio (games, skype, music, movie);
- input voice and analog audio to computer (skype, music editors);
- for creation of music (input and output sound created in music editors - a.k.a. DAW - Digital Audio Workstation);
- connecting hardware MIDI-instruments.

Connecting to sound card

Connection sound cards to computer:

1 Internal:
1.1 Built in motherboard;
1.2 Installed in sockets of motherboard:
- PCI;
- PCIe (PCI Express).
2 External:
2.1 USB;
2.2 FireWire (IEEE 1394).

Inside sound card

Sound Card Inside





Parts of sound card:

1 Analog filter before analog-digital converter (ADC) - for suppression of conversion artefacts. Ultrasound components of signal (lying over 1/2 of sample rate) are shifted to audible range. It perceived as noise or whistle;

2 Analog-digital converter transform analog signal (microphone, guitar, synthesizer analog inputs) to a digital form;

3 Controller of computer interface - passes digital signal to/from computer buses PCI, PCIe, USB, FireWire;

4 Digital-analog converter (DAC) - transform digital signal from computer to output analog signal;

5 Analog filter after DAC suppress conversion (digital signal to analog) artefacts.

6 Input and output balanced circuits - for suppression of interference (for some cards only).

Sound card may have processing module for changing sampling frequencies, apply effects, etc. "on fly".


About audio card PCI and PCIe here...