AC'97

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AC'97 (short for Audio Codec '97) is an audio standard that was developed by the Intel Architecture Labs in 1997 and is mainly used by on-board chips for mainboards, less often modems and sound cards . The successor is the High Definition Audio Interface .

construction

Sound card with AC'97 codec

Chipsets with integrated audio components contain two, optionally three components:

  • AC'97 digital controller, which is coupled to the PCI bus in the I / O controller hub (ICH) of the chipset and controls the external AC'97 analog codec module via its own bus, AC-Link, and optionally a proprietary socketed CNR or AMR card (Audio and Modem Riser).
  • AC'97 analog codec, which integrates the analog mixer and the ( PCM ) digital-to-analog converter ( DAC ) and the analog-to-digital converter ( ADC ).
  • OEM Riser Slot & Card: AMR or CNR.

The standard defines an audio architecture for the PC , which was installed by various manufacturers for various chipsets as an inexpensive minimum equipment with multimedia capabilities. Pin contact strips on main boards for coupling front panels (FP audio) which, in contrast to the connections on the AC'97-2.3-compliant main board, are not designed for jack sensing, are also identified as legacy AC'97 . Pin contact strips that are designed for jack sensing in accordance with AC'97 Rev. 2.3 are referred to as HD audio . Jack sensing requires sockets of different electromechanical design, in which the plug does not separate the empty contact, but closes an isolated switch. In 2004, the AC'97 standard was replaced by Intel's High Definition Audio Interface (HD audio for short).

Versions

  • AC'97 1.x -compliant: Sampling rate fix 48 kHz, 16-bit full duplex audio codecs (DAC, ADC), microphone input (MIC1) with 20 dB preamplifier and supply voltage (with a maximum load of 5 mA) for electret microphones (MIC_BIAS), mono output (MONO_OUT) for telephone or internal loudspeaker (SPKR), stereo output (LINE_OUT), proprietary modem support (LINE1 I / O, GPIO), no optional extensions (2.1: extended audio, extended modem feature set ; 2.2: enhanced riser audio; 2.3: extended configuration information).
  • AC'97 2.1 -compliant: optional variable sampling rate (rate conversion can be done in software by the driver, in hardware 48 kHz and 44.1 kHz, optionally doubled to 88.2 kHz or 96 kHz), optionally 18 or 20 bit codec resolution (not for phone), multi-channel sound (second stereo output (AUX_OUT), configurable as second output or optionally as 4 or 6-channel output (LINE_OUT + 4CH_OUT + AUX_OUT, optionally with 3D stereo extension)) , optionally a third stereo input channel, standardized modem support.
  • AC'97 2.2 -compliant: extended support for AMR cards: optional support for a second telephone connection (LINE2 I / O, HSET I / O); optional S / PDIF for 5.1 Dolby Digital Audio (AC-3). However, there are a number of reasons why this feature only works as an upgrade to the list of features.
  • AC'97 2.3 -compliant: optional jack sensing that uses suitable connection sockets to inform the driver about the presence and type (passive speakers, headphones, amplifier, microphone) of a device connected to the socket and thus allows a suitable automatic configuration of the respective connection (audio -Plug-and-Play).

Not all connections on a standard-compliant chip are always available as connections on every board marked as standard-compliant. The AC'97 standard does not prescribe how any connection sockets should be implemented. A version of the connection sockets as 3.5 mm jack plugs results implicitly from Intel's Front Panel I / O Connectivity Design Guide .

Microphone connection problem

An AC'97 microphone connection for a jack plug supplies supply voltage (MIC_BIAS) to the middle contact. If a mono plug (two-pin) is inserted, the supply voltage is pulled to ground. The short circuit must not lead to electrical damage if this state corresponds to the setting "No front panel connected".

A mono electret microphone with a mono plug expects a tone feed at the plug tip. The plug tip only supplies AC'97 with supply voltage if stereo microphones are supported. Electret microphones require the supply voltage. Dynamic microphones, on the other hand, must not be supplied with supply voltage.

AC'97 audio connector

Plug contact

The AC'97 audio plug-in contact is designed as a ten-pole pin strip with not necessarily always the same pinout .

AUD_GND, AGND, analog GND
Ground for audio circuits (isolated from shield )
MIC, MIC2, MIC input
Microphone input (if stereo microphones are supported: plus audio feed)
MIC_BIAS, MIC_PWR, MIC power
Microphone power supply (if stereo microphones are supported: audio cable power supply plus second microphone input)
AUD_5V, + 5VA, analog VCC
smoothed or interference-filtered +5 V for supplying audio circuits; However, there is no information on the load capacity of AUD_5V, and measurements show that AUD_5V is not necessarily actually smoothed.
FP_OUT_R, LINE_OUT_R, Right line output
Audio output (LINE_OUT) right (line or headphones)
FP_RETURN_R, BLINE_OUT_R, Right line return
from the front panel back to the LINE_OUT socket on the right side of the board, with the jack plugged in: open
FP_OUT_L, LINE_OUT_L, Left line output
Audio output (LINE_OUT) left (line or headphones)
FP_RETURN_L, BLINE_OUT_Lv, Left line return
from the front panel back to the LINE_OUT socket on the left on the board, with the jack inserted: open

If no front panel is connected, contacts must be bridged.

1. To supply the onboard LINE_OUT on the back panel :
FP_RETURN_L = FP_OUT_L
FP_RETURN_R = FP_OUT_R
2. To stabilize the microphone amplifier against drift, if necessary, which is noticeable in crosstalk and noise in the backpanel microphone channel:
MIC = GND
MIC_BIAS = GND
In the case of pinout variants where MIC_BIAS is next to AUD_5V, this bridging cannot be made using jumpers . It is not carried out there at the factory.

Connection cable

The connection cable should be approx. 45 cm long (17.75 ″ ± 0.25 ″) and consist of four twisted AWG -26 pairs (conductor cross-section 0.14 mm²) with a shared shield made of braiding and foil ( SF / STP cable).

Form a pair each:

FP_RETURN_L - FP_OUT_L
FP_RETURN_R - FP_OUT_R
MIC_BIAS - MIC
AUD_5V - AUD_GND

To avoid a hum loop , the shield must not be connected to AUD_GND even if a second AUD_GND pin is provided. It must only be connected to the housing on the side of the front panel.

Web links

Commons : AC'97  - collection of images, videos and audio files

Individual evidence

  1. ↑ Intel Corporation: AC'97 Component Specification (PDF; 1.2 MB), Revision 2.3, April 2002, 1.4
  2. ↑ a b Front Panel I / O Connectivity Design Guide ( Memento of the original from May 11, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 654 kB), Intel Corporation, February 2005, Version 1.3, 2.3.4 @1@ 2Template: Webachiv / IABot / www.formfactors.org
  3. ↑ a b c z. B. ASUSTeK Computer Inc. ( Memento from February 10, 2013 in the web archive archive.today ): A8N-SLI Premium User Guide, company publication E2128, 2nd revised edition, ROC Taiwan 2005, 13
  4. ↑ Front Panel I / O Connectivity Design Guide ( Memento of the original from May 11, 2011 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 654 kB), Intel Corporation, February 2005, Version 1.3, 2.3.5 @1@ 2Template: Webachiv / IABot / www.formfactors.org
  5. ↑ Front Panel I / O Connectivity Design Guide ( Memento of the original from May 11, 2011 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 654 kB), Intel Corporation, February 2005, Version 1.3, 2.3.3 @1@ 2Template: Webachiv / IABot / www.formfactors.org
  6. ↑ a b Front Panel I / O Connectivity Design Guide ( Memento of the original from May 11, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 654 kB), Intel Corporation, February 2005, Version 1.3, Figure 2 @1@ 2Template: Webachiv / IABot / www.formfactors.org
  7. ↑ Front Panel I / O Connectivity Design Guide ( Memento of the original from May 11, 2011 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 654 kB), Intel Corporation, February 2005, Version 1.3, Figure 6 @1@ 2Template: Webachiv / IABot / www.formfactors.org
  8. ↑ a b Intel Corporation: AC'97 Component Specification (PDF; 1.2 MB), Revision 2.3, April 2002, 1.1–1.3
  9. ↑ Intel Corporation: AC'97 Component Specification (PDF; 1.2 MB), Revision 2.3, April 2002, 2.3.5
  10. ↑ Intel Corporation: AC'97 Component Specification (PDF; 1.2 MB), Revision 2.3, April 2002, 1.5
  11. ↑ Intel Corporation: AC'97 Component Specification (PDF; 1.2 MB), Revision 2.3, April 2002, 1.1, 1.4
  12. ↑ Intel Corporation: AC'97 Component Specification (PDF; 1.2 MB), Revision 2.3, April 2002, 5.10
  13. ↑ Intel Corporation: AC'97 Component Specification (PDF; 1.2 MB), Revision 2.3, April 2002, 1.1
  14. ↑ Intel Corporation: AC'97 Component Specification (PDF; 1.2 MB), Revision 2.3, April 2002
  15. ↑ a b c Front Panel I / O Connectivity Design Guide ( Memento of the original dated May 11, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 654 kB), Intel Corporation, February 2005, Version 1.3, 2.3.4.4 @1@ 2Template: Webachiv / IABot / www.formfactors.org
  16. ↑ Front Panel I / O Connectivity Design Guide ( Memento of the original from May 11, 2011 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 654 kB), Intel Corporation, February 2005, Version 1.3, Table 6 @1@ 2Template: Webachiv / IABot / www.formfactors.org
  17. ↑ a b c d e f g h i Front Panel I / O Connectivity Design Guide ( Memento of the original from May 11, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 654 kB), Intel Corporation, February 2005, Version 1.3, 2.3.4.3 @1@ 2Template: Webachiv / IABot / www.formfactors.org
  18. ↑ Front Panel I / O Connectivity Design Guide ( Memento of the original from May 11, 2011 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 654 kB), Intel Corporation, February 2005, Version 1.3, Figure 3 @1@ 2Template: Webachiv / IABot / www.formfactors.org
  19. ↑ z. B. Tyan Computer Corporation: Thunder i7505 / S2665 Manual , company publication , 2002, 2.14
  20. ↑ a b c d e f g h ASUSTeK Computer Inc .: A8N-SLI Premium User Guide, company publication E2128, 2nd revised edition, ROC Taiwan 2005, 13
  21. ↑ a b c d e f g h Tyan Computer Corporation: Thunder i7505 / S2665 Manual , company publication , 2002, 2.14
  22. ↑ a b Front Panel I / O Connectivity Design Guide ( Memento of the original from May 11, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 654 kB), Intel Corporation, February 2005, Version 1.3, 4.3.2 @1@ 2Template: Webachiv / IABot / www.formfactors.org
  23. ↑ Front Panel I / O Connectivity Design Guide ( Memento of the original from May 11, 2011 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 654 kB), Intel Corporation, February 2005, Figure 12, 4.3.2 @1@ 2Template: Webachiv / IABot / www.formfactors.org