Sound card

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PCI sound card with integrated Firewire interface

A sound card ( English Sound Card ) - and audio card , rare sound card - is an optional component of the hardware of a computer , the analog and digital audio signals processed. Originally the term referred to a plug-in card that was connected to the data bus of a PC . So-called onboard audio chips are now also counted among the sound cards because they have the same function.

The tasks of a sound card include the recording , generation , mixing, processing and reproduction of sound signals. Occasionally, sound cards are also used as a measuring device. Depending on the type, analog and digital sound sources and processors can be connected, as well as expansion cards and synchronization sources in professional systems. The connection to the PC takes place via the PCI or PCI Express bus (with older sound cards via the ISA bus) or with notebooks via the PCMCIA or ExpressCard slot. External sound cards are connected via the USB interface, in the professional sector also via FireWire or Thunderbolt , as well as MADI . Some sound cards store the connection field in a front module (5.25 ″ insert, see form factor ) or an external housing, the so-called breakout box .

In the 2000s, the typical sound card changed from a plug-in card to a microchip integrated on the motherboard (onboard audio) in the course of advancing electronics integration. An example is AC'97 or HD audio integrated in the chipset . However, dedicated plug-in cards are still in use for users who have a higher demand for sound quality or computing power or need more extensive connection options. If the card has its own DSP , this also reduces the load on the main processor .


Unlike 1980s home computers , which often had built-in sound chips , personal computers had no music or sound capabilities. The first sound cards appeared on the market for the Apple II from 1983 (e.g. mocking board ), but were still niche products that were only supported by relatively few games. They were pure synthesis cards ; the playback of samples was not yet feasible due to the small memory at the time. They became popular in the PC sector from around 1989/90, when the AdLib and Sound Blaster cards first developed a standard that went beyond simple system loudspeakers .

While the first models followed the development in the PC sector that had already been carried out years before in the home computer sector, the sound capabilities of the PC sound cards already went up with the appearance of the Roland LAPC-I , which, however, also cost around 1,000 DM (based on today's purchasing power about 880 euros), beyond that of the home computer. That was a major factor in the collapse of the home computer market and the takeover of the “gaming computer” market position by the PCs, which previously served almost exclusively as office computers.

Sound cards manufactured up to around the year 2000 usually have a game port . The Sound Blaster 1.0 from 1989 was the first to be equipped with such an additional connection, which was primarily intended for one or two analog joysticks . Alternatively, the game port could also be used to connect external MIDI devices ( MIDI port ), although in the 1990s it was mainly used as a game port for computer games. When CD-ROM drives for PCs appeared around 1990, many sound cards were also equipped with a connection for CD-ROM drives. Since there was no standard, proprietary , manufacturer-specific connections from Mitsumi , Panasonic or Sony were used in the beginning , including the more expensive SCSI connection. However , it was not possible to start from a bootable CD-ROM because the firmware (the BIOS ) of the PCs could not address the various drives - the device drivers supplied did not work until the operating system was started. From 1997 onwards, ATA / ATAPI-4 became a manufacturer-independent interface that quickly replaced proprietary connections. On later motherboards , two plug-and-play and bootable ATA / IDE channels prevailed, so that the additional CD-ROM controllers of the sound cards caused compatibility problems if they could not be deactivated by jumpers , because they would use the same resource, e.g. B. the second IDE channel ( "secondary IDE" : IRQ 15, IO-base 0x170), was occupied by both controllers and thus blocked. The connection for the analog transmission of audio signals from the CD-ROM drive to the sound card, which is also found on the motherboard of onboard sound chips, has been retained.

The Gravis Ultrasound PC sound card, released in the early 1990s, offered hardware mixing with up to 32 hardware output channels and panning, but was unable to establish itself on the market (except in the demo scene , for example with musicians on trackers ). On the one hand, because it was not completely compatible with the prevailing sound cards, and also because the more economical software mixing of the Sound Blaster cards became established with increasing computing power . Hardware mixers have slowly become uncommon in the home multimedia segment. Since then, an increasing separation and delimitation of the market segments can be observed. More on this in the Consumer, Professional and Onboard section.

At first most sound cards were more or less direct replicas of a few less common models, but this changed after the introduction of Windows 95 . Since Windows -based games no longer had to address the hardware of the sound card directly, like the DOS -based PC games before , but instead took place via standardized device drivers , there were hardly any limits to the hardware structure of the cards.

There are many more different sound cards than sound chipsets on the market. Many high-quality sound cards from different manufacturers use, for example, the envy24 codec chipset , which has been manufactured largely unchanged since the late 1990s and enables a wide range of concepts (the 1712 variant even has a 36-bit hardware mixer for professional studio solutions)

Since around the year 2000, the basic audio functions have been integrated in most motherboards, so that separate (dedicated) sound cards were only used if there were higher demands on quality or functionality. In the meantime, even HD audio codecs - such as B. the ALC888 and the ALC889 from the IC manufacturer Realtek - used for the so-called "onboard sound" solutions. If you disregard Creative's X-Fi series and a few other models from other manufacturers, then these chips are much more powerful than most well-known sound cards and especially than older sound codecs of the AdLib and Sound Blaster 16 era. The weak point in sound output on the computer (especially with mobile devices) are now the amplifiers and speakers.

Computers are also increasingly used for professional music productions. Since the beginning of the 1990s, computing power and RAM have been sufficient for signal processing in comparatively cheap computers. The combination of PC and high-quality sound card or chipset has since largely replaced the previously customary specialized devices for recording, editing and processing sound material in the studio. In order to achieve a signal quality appropriate for studio production, so-called audio interfaces are often used, which are not built directly into the computer. They are usually connected to the computer via a FireWire or USB cable or via a special digital interface card with a breakout cable. By decoupling the audio signals from the rest of the PC and its interfering signals as well as other technical measures, a sound quality is achieved that also meets professional requirements. Both IBM PC-compatible and Macintosh computers are suitable for music production . The latter are (supported by rumors and marketing) as being particularly optimized for audio processing. Audio cards intended for professional use can usually be used with both Macs and PCs.

The manufacturers offer driver software for both simple and professional sound cards for the Windows and macOS operating systems (originally under the name “Mac OS X”). Free projects develop drivers with which many professional and most simple sound cards can now also be used with Linux , whereby in some cases not all functions of the sound card can be used.



Sound processor

The basis of audio signal processing in the PC is an audio codec chipset such as the VIA Envy24 mentioned above, which receives data and control signals from the central computer system from the sound card driver via an internal computer bus system (e.g. PCIe) and transfers a continuous data stream format understandable for a D / A converter , e.g. B. I²S translated. The analog audio signals at the input are digitized by an A / D converter and passed on to the codec, which then sends them to the operating system driver via a bus system. Both converters are often integrated on the same chip in cards. Modern onboard solutions even get by with just a single component.

Entrances and exits

There are different types of inputs and outputs: analog, digital or via MIDI .


There are analog inputs / outputs in the form of jack sockets or cinch sockets . In modern non-professional cards, as well as on ATX - motherboards with integrated sound chip or the audio jacks on the front panel of modern computers, these sockets in addition to an impressed typically symbol color-coded according to international standards (see color code ).

Standard connections of an integrated sound chip
colour function
  pink Input for microphone ( mono ).
  green Line-out / output for headphones or (front) speakers (stereo)
  blue Line-in / input for AUX / external sources ( stereo ).
  Gray Output for side speakers side speakers ] (stereo)
  orange Output for center and sub-bass speakers center speaker, subwoofer ]
  black Output for rear speakers rear speakers ] (stereo)
color-coded connections on a sound card (year 2008)
colour function
  White Output for side speakers side speakers ] (stereo)
  blue Line-in / input for AUX / external sources ( stereo ).
  pink Input for microphone ( mono ).
  green Line-out / output for headphones or (front) speakers (stereo)
  black Output for rear speakers rear speakers ] (stereo)
  orange Output for center and sub-bass speakers center speaker, subwoofer ]

While the jack sockets (with the exception of the microphone input) on non-professional cards are usually designed for forwarding stereo signals, with professional cards only one mono signal is forwarded per jack socket using symmetrical transmission technology .

Technical data of the audio inputs:

  • LINE-IN: Standard level 1 volt (depending on the sound card ± 0.7 volts up to | U ss | max. 2 volts), input resistance 20 ... 70 kOhm
  • MIC-IN: maximum input level depending on the sound card from 20 mV to max. -100 ... + 100 mV (see also microphone input )
  • LINE-OUT: 1 volt standard level (depending on the sound card ± 0.7 volts up to | U ss | max. 2 volts, source resistance <50 ohms to 1 kOhm)
  • AD / DA converter resolution: up to 32 bit,
  • Sampling rate: variable up to 192 kHz (depending on the sound card)

Sampling rates of 44.1 or 48 kHz are sufficient for conversion into low-frequency signals (audible limit 20 kHz) according to the sampling theorem - higher sampling rates hardly increase the quality of audio signals. In general, oversampling can make sense in the A / D conversion (digitization) if the signal contains relevant high components> 20 kHz, because these could not be filtered out sufficiently and they should be retained, e.g. B. with square wave signals.

CD-ROM analog input
Analog audio output from an internal CD-ROM drive

Many CD-ROM drives for the PC are also stand-alone audio CD players. Some internal 5.25 "drives from the 1990s even had their own play button, and even later, almost all internal optical drives have a 3.5 mm headphone jack on the front. With an audio CD inserted, playback can be started either by software or with the button, the D / A converter built into the drive forwards the sound in analog form via the front jack and the internal output. This works without the involvement of the computer and is therefore completely independent of the PC's CPU . In order for the output to work via the boxes connected to the sound card, the CD-ROM drive must be connected to the sound card on the back with an audio cable, whereby there are different standards. Because this type of sound output works without additional load on the processor, some computer games of this time used a mixed-mode CD : Only the first track contains data, such as the installation program. If the game is started from the hard drive, the game music comes from the audio tracks on the CD. If this is missing, either the computer game refuses to start or there is an easier substitute, usually in the form of music from a MIDI file.

Sound cards and motherboards with onboard audio chips therefore often have one of the different 2-, 3- or 4-pin analog audio sockets, which are often CD_INlabeled with. The 4-pin connector with RGGL assignment finally prevailed rechter Kanal - Masse - Masse - linker Kanal.

Microphone input

The microphone inputs of simple sound cards or onboard "sound cards" are usually not sufficiently sensitive to reproduce signals from dynamic microphones (often below 1 mV) sufficiently well.

According to the AC'97 standard, there is a 20 dB preamplifier behind the microphone input (10-fold voltage gain).

Electret microphones with a built-in impedance converter deliver a sufficient level (a few 10 mV), but - if they do not have their own power supply - they need a so-called audio supply .

For this purpose, with AC'97-compatible sound cards (see AC'97 standard: microphone connection problem ) the middle ring of the jack socket of the microphone input supplies a voltage (5 volts) via a resistor (approx. 1… 2 kOhm). The tip of the microphone jack plug makes contact with the microphone signal input.

  • Two-pole electret microphones can connect the middle ring with the contact at the tip (signal input) and work on the resistance in the PC as a working resistance (see emitter circuit )
  • Electret microphone solutions for a better signal-to-noise ratio first screen this voltage, which is often noisy, and use its own working resistor.
  • Mono (microphone) jack plugs short-circuit the tone supply without damage

Due to the low voltage, the AC'97 audio supply cannot be used as phantom power for the amplifiers of condenser microphones and at 5 volts it is also lower than the T-12 standard (12 volts) for a “real” audio supply.

Dynamic microphones with stereo plugs or symmetrical jack plugs are not damaged by the current-limited voltage of this tone wire supply, which is limited to a few milliamps, but usually require an external microphone preamplifier .


Sound cards can also have digital inputs / outputs for audio and MIDI signals.

MIDI and game port
MIDI cable for the game port of the AWE Sound Blaster card from Creative

Some sound cards also contain a game port , usually with a MIDI connection on the same socket. The data transfer via the game port works analogously when used as a game controller (e.g. joysticks or gamepads ), digitally when used as a MIDI connection. In the past, this game port was available on almost all sound cards; most modern sound cards do not have it, as newer game controllers are usually connected to the computer via the USB interface and Windows Vista and higher no longer supports the game port.


Some sound cards contain a Sony / Philips digital interface ( S / PDIF , cable or optical fiber). This is designed either in optical or coaxial form. Professional systems use the AES / EBU format with an XLR connector. However, this must not be confused with an analog XLR connection. A stereo signal can be transmitted via the interface. You need separate sockets for sending and receiving.


Sound cards for recording studio applications often have an ADAT interface through which up to 8 channels (4 stereo channels) can be transmitted simultaneously in one direction. An optical TosLink interface is used here. Some cards can be switched between 8-channel and 2-channel S / PDIF operation.


The TDIF interface can also be found on some cards. 16 channels can be transmitted in both directions at the same time. A wired cable interface is used here.

Connection expansions

Front of the breakout box of a sound card (2006)

With some models, the limited space on a slot bracket is provided with additional cable whips (a special cable with many connection options that occupies the joystick port) or a " breakout box " (an additional module in the form of a slot for a 5.25 "slot or an external housing).

Sometimes an additional slot cover is used, which is connected to the sound card with a cable inside the housing.

Other extensions

Sound cards that have their own sound generation can occasionally be expanded with wavetable modules .


In terms of quality, converter cards differ in the possible bit resolution ( word length , 8 bit, 16 bit or 24 bit), maximum sampling rate (e.g. 22, 44, 96, 192 or 384  kHz ), noise behavior, frequency response, and shielding against internal computer interference and the maximum number of channels.

Many sound cards support different sound output standards such as EAX , DTS -ES, or ASIO . In contrast to the onboard variants, today's normal sound cards also have an accelerator chip, which relieves the CPU of some of the computing work. However, some cheap sound cards do without it.

Consumer cards

Simple PCI sound card

Until about the end of the 1990s, these cards often still contained an FM synthesizer chip, which enabled electronic music to be played through sound synthesis and without the use of samples (digitized sounds), which greatly reduced the computing requirements and memory consumption in the PC, but also less was more flexible than sample-based playback. The next step to improve the sound quality was the implementation of a uniform interface to expand the sound card using a wavetable .

Due to the steadily increasing computing power and memory size, FM or wavetable synthesis is now performed on the software side using software synthesizers . This made the FM synthesizer chip and the wavetable expansion option largely unnecessary.

Professional cards

M-Audio delta 1010 audio interface with external converters
Soundscape Mixtreme PCI card with TDIF connector and integrated DSP chip

Professional cards that are used in recording studios and DAWs are also known as recording cards or audio interfaces. Such cards can usually record several channels separately, which is necessary, for example, when recording drums or recording several musicians or sound sources at the same time . In principle, you can work full-duplex, i.e. play back and record simultaneously. This enables z. B. the integration of external physical effects devices into the production setup. In addition, higher quality A / D and D / A converters are used than with consumer sound cards. In addition, the special features of EMC are taken into account in the layout of the circuit board and the analog circuit parts are appropriately shielded. The quality of the recorded signal is in the foreground in this market segment; the usual game port for connecting a joystick on consumer sound cards is not available on professional cards. The MIDI interface, which is otherwise realized in the multimedia area in the game port, is implemented in a professional manner. Consumer effects such as karaoke functions or 3D simulations for games (e.g. EAX) are usually not available.

To avoid interfering noises from electromagnetic fields inside the computer, the A / D and D / A converters in some systems are housed in external housings, for example as a breakout box . Furthermore, the drivers of such audio interfaces usually allow freely definable routing of the incoming and outgoing signals. The drivers also support software interfaces with low latency, such as ASIO / EASI / GSIF etc. and offer functions such as B. Latency-free preview. These drivers are optimized for the hardware and can therefore be significantly more powerful and flexible than standard Windows interfaces and software adapters (e.g. Asio4All). High-quality microphone preamps with phantom power or inputs for instruments (High-Z) for professional music production are also integrated. In addition to analog and digital inputs and outputs in S / PDIF format, there are also multichannel digital audio interfaces in ADAT and AES / EBU or (more rarely) TDIF and / or MADI , via which the card can be connected to external converters and digital mixers .

Some models (for example the Pro Tools / TDM system, which is widely used in the professional sector ) as well as the systems from Universal Audio, Sonic Core / Creamware, Solid State Logic and Soundscape also contain DSP chips, which do all the processing and mixing of the data streams including complex effects and instruments directly on the card and thus do not burden the main processor of the computer. The cards can therefore work completely independently; the effects and the mixing settings are only set by the PC software, so the majority of the CPU power is available for a fast user interface (GUI), background services and control commands (controller automation and parameter control) and for the operating system, so that the System remains operable and responsive for the user.

Sound chip on the motherboard

AnalogDevices AD1888 AC'97

The first attempts to integrate a sound chip on IA-32 compatible motherboards ("onboard sound chip") were made at the end of the 1990s. These are motherboards with Super Socket 7 for AMD K6-2 processors or slot 1 for Intel Pentium II processors. These sound chips are ISA PnP devices, the configuration of which turned out to be problematic. The functionality of these first sound chips was limited to stereo audio playback and inputs for line level and microphone, whereby the microphone input in particular is often practically unusable due to strong interference. The recording and playback quality can be set to a maximum of “Stereo 44.1 kHz 16-Bit”. A MIDI / game port interface was also provided.

Onboard sound chips integrated on the motherboard, which mostly corresponded to the AC'97 standard, increasingly supplanted additional sound cards in their basic functions. These sound chips are PCI devices, which simplifies the configuration compared to an ISA-PnP variant. In the beginning, onboard sound chips offered no more functionality than comparable ISA PnP sound cards, but with the HD audio available from 2004 , additional functions were added and the quality improved. Depending on the implementation, onboard sound chips have since offered 7.1 audio playback, inputs for S / PDIF, high level and microphone, so that no additional sound card is required for most applications. The previously common MIDI / game port interface, however, has been omitted. For upgrading, for example when a second sound card is required or for systems without an integrated sound chip, e.g. For example, older PCs or embedded PCs have dedicated sound cards. Also in the professional and audiophile market there are still specialized sound cards. B. achieve better quality and / or offer more functions, such as interfaces such as a MIDI port.

External audio devices

USB sound cards with and without cables
Back of a professional audio interface with connections for PC, MIDI, S / PDIF and ADAT

Although often referred to as a sound card, external audio devices are no longer expansion cards (as was the original meaning of sound card ), but rather completely stand-alone devices. External solutions offer even more independence from operating systems and (dedicated) drivers, as they are connected to the PC via USB or FireWire, for example , and use the defined standards of the interface, such as the corresponding USB device class .

Simple sound inputs / outputs are possible with inexpensive USB sound cards, often as a USB stick in size and shape, which offer roughly the same performance as onboard sound cards. With better models, all important electronic components are housed in an external housing to avoid interference and, compared to onboard sound chips, offer additional functions and additional connections. It is not uncommon for external sound cards to be combined with amplifiers .

In professional systems, the electronic circuit board is usually of higher quality, has more layers and its own power supply, and professional connections such as word clock , symmetrical analog inputs and grounding options are available. In some cases, these no longer necessarily have to be connected to the PC in order to function.

For a direct connection to the PC, audio devices must still be connected via the data bus , either as a plug-in card or externally via Thunderbolt or USB-C . Device-specific drivers are still required for this. In the case of professional systems, these are often specially optimized by the manufacturer for the hardware and are correspondingly powerful.

Manufacturer (selection)

Consumer hardware
Professional sound cards / audio interfaces

Web links

Wiktionary: Sound card  - explanations of meanings, word origins, synonyms, translations
Commons : sound card  - collection of pictures, videos and audio files
  • Stefan Göhler: Phenomenal! ... a look back at the history of sound cards , 1981 to 1995 with sound samples , on (2004)
  • Jürgen Schuhmacher: Sound for professionals (PDF file; 489 kB) Article on computer sound cards in the PC-Games-Hardware magazine (2001)

Individual evidence

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  2. Michael Meister: Design and implementation of a scalable multimedia laboratory based on modern didactic concepts ., 2006, ISBN 978-3-8324-9787-3 ( limited preview in the Google book search).
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  14. Patrick Schnabel: AC-97. Electronics Compendium, 2020, accessed July 7, 2020 .
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  16. Patrick Schnabel: Game port / MIDI port / interface. Electronics Compendium, 2020, accessed July 7, 2020 .
  17. Dr. Andreas Hau: USB audio interface - purchase advice. In: . April 12, 2020, accessed on July 7, 2020 (German).