pctechguide.com

Sound Card Components

The modern PC sound card contains several hardware systems relating to the production and capture of audio, the two main audio subsystems being for digital audio capture and replay and music synthesis along with some glue hardware. Historically, the replay and music synthesis subsystem has produced sound waves in one of two ways:

  • through an internal FM synthesiser
  • by playing a digitised, or sampled, sound.

The digital audio section of a sound card consists of a matched pair of 16-bit digital-to-analogue (DAC) and analogue-to-digital (ADC) converters and a programmable sample rate generator. The computer reads the sample data to or from the converters. The sample rate generator clocks the converters and is controlled by the PC. While it can be any frequency above 5kHz, it’s usually a fraction of 44.1kHz.

Sound

Most cards use one or more Direct Memory Access (DMA) channels to read and write the digital audio data to and from the audio hardware. DMA-based cards that implement simultaneous recording and playback (or full duplex operation) use two channels, increasing the complexity of installation and the potential for DMA clashes with other hardware. Some cards also provide a direct digital output using an optical or coaxial S/PDIF connection.

A card’s sound generator is based on a custom Digital Signal Processor (DSP) that replays the required musical notes by multiplexing reads from different areas of the wavetable memory at differing speeds to give the required pitches. The maximum number of notes available is related to the processing power available in the DSP and is referred to as the card’s polyphony.

DSPs use complex algorithms to create effects such as reverb, chorus and delay. Reverb gives the impression that the instruments are being played in large concert halls. Chorus is used to give the impression that many instruments are playing at once when in fact there’s only one. Adding a stereo delay to a guitar part, for example, can thicken the texture and give it a spacious stereo presence.

Filed Under: Sound Cards

Latest Articles

Object Oriented Programming – Examples

Earlier we developed a class inheritance tree for some game characters in a maze game, but we need to design another class, or class hierarchy, for the maze. Since we want the mazes to have different levels of difficulty, each level of maze will require slightly different functions. We can … [Read More...]

Communication Speeds

The actual speed at which a modem can operate is dependent on the particular obstacles it has to overcome. These include: the PC itself, and in particular its serial port the state of the telephone line the kind of modem it is connecting to at the other … [Read More...]

VXA Tape Storage technology

Streaming is the technique used to transfer data in linear and helical scan tape drives, which operate by reading an entire track thousands of bytes long in a single pass of a Read head at a fixed tape speed. In order for such drives to operate … [Read More...]

Guides

Recent Posts