PC audio connectors

External

Analog PC audio (soundcard) uses mini jacks;

    _
   / \
   \ /   <-- Tip
   ===
   | |   <-- Ring
   ===
   | |
   | |   <-- Sleeve
   | |
   | |
  =====

General

 Left    Tip
 Right   Ring
 GND     Sleeve

Colour codes

Inputs

 Pink   Mic
 Blue   Line

Outputs

 Green  Main / Front
 Brown  Side
 Black  Rear
 Orange Center / Subwoofer

Electret microfones

Signal from source

Also known as a source follower of common drain amplifier.

                        +---------> + 5 V
                        |
                        |
                    | d |
                    |---+
     --   |         |      Fet
   /    \ |-------->|---+
  |  ||  ||       g | s |
   \    / |---+         |
     --   |   |         |   | |
              |         *---+ +---> Audio
  electret    |         |   | |
    mic       |         |
              |         |
              |        +++
              |        | | 2.2 kΩ
              |        +++
              |         |
              |         |
              |         |
              +---------*---------> GND

This system is incompatible with PC microphone inputs. You need a pre amplifier and power source to make this work.

Signal from drain

Also known as a common source amplifier.

                        +---------> + 5 V
                        |
                        |
                        |
                       +++
                       | | 2.2 kΩ
                       +++
                        |
                        |
                        |   | |
                        *---+ +---> Audio
                        |   | |
                        |
                    | d |
                    |---+
     --   |         |      Fet
   /    \ |-------->|---+
  |  ||  ||       g | s |
   \    / |---+         |
     --   |   |         |
              |         |
  electret    |         |
    mic       +---------*--------> GND

This is compatible with mic in.

Mono mic

                                              +---+
                        +--------> Ring <-----+   +-----> + 5 V
                        |                     +---+
                        |                      2k2
                        |
                        |                      | |
                        *--------> Tip  <------+ +------> Audio
                        |                      | |
                        |
                        |
                        |
                    | d |
                    |---+
     --   |         |      Fet
   /    \ |-------->|---+
  |  ||  ||       g | s |
   \    / |---+         |
     --   |   |         |
              |         |
  electret    |         |
    mic       +---------*--------> GND / <--------------> GND
                                   Shield /
                                   Sleeve

Stereo mic

Left:

                                                +---+
                                            +---+   +---> + 5 V
                                            |   +---+
                                            |    2k2
                                            |
                                            |    | |
                        +--------> Tip  <---*----+ +----> Audio
                        |                        | |
                        |
                        |
                        |
                    | d |
                    |---+
     --   |         |      Fet
   /    \ |-------->|---+
  |  ||  ||       g | s |
   \    / |---+         |
     --   |   |         |
              |         |
  electret    |         |
    mic       +---------*--------> GND / <-------------> GND
     L                             Shield /
                                   Sleeve

Right:

                                                +---+
                                            +---+   +---> + 5 V
                                            |   +---+
                                            |    2k2
                                            |
                                            |    | |
                        +--------> Ring <---*----+ +----> Audio
                        |                        | |
                        |
                        |
                        |
                    | d |
                    |---+
     --   |         |      Fet
   /    \ |-------->|---+
  |  ||  ||       g | s |
   \    / |---+         |
     --   |   |         |
              |         |
  electret    |         |
    mic       +---------*--------> GND / <-------------> GND
     R                             Shield /
                                   Sleeve

Internal

Audio frontpanel

Wikipedia: Intel High Definition Audio

AC'97 and HD audio front panel layouts;

CDROM to soundcard

3 pin

pin 1 - Left signal output
pin 2 - Ground
pin 3 - Right signal output

4 pin

pin 1 - left signal
pin 2 - ground
pin 3 - ground
pin 4 - right signal

Or

pin 1 - left signal
pin 2 - ground
pin 3 - right signal
pin 4 - ground