Enabling Input Audio Monitoring on Dell Latitude D820

I recently re-installed XP on my Dell Latitude
D820 for the third time in 2 years and ran into a familiar problem: My
line-in audio was not being played through the speakers. By default,
the Dell driver, R171789 (SIGMATEL STAC 92XX C-Major HD Audio) does not
come with the input monitor enabled. You can modify the driver INI
file(s) manually to enable this and other related options.

Backup these files (make a copy in the same directory named 92XXM2-2.INI.orig):
    C:\DELL\drivers\R171789\WDM\92XXM2-2.INI
    C:\Program Files\SigmaTel\C-Major Audio\WDM\92XXM2-2.INI
    C:\Program Files\SigmaTel\C-Major Audio\DellXPM_5515v131\WDM\92XXM2-2.INI

Edit each one and change the following settings to reflect what is shown:
    EnableInputMonitor    = hex: 1
    DigitalInputMonitor     = hex: 1
Additionally you can/should turn on these options that allow for greater control of the sound card options:
    To see all of the config tabs (that I know of):
       Config_Tab = dword: 0x000000ff
    To see all of the Advanced config options:
       Config_Adv = dword: 0x000fffff
    To allow sample rate adjustment:
       Config_Rates = dword: 0x000000ff
    To disable automatic input switching (helps avoid feedback)
       RecordPriority = dword: 0xffffffff
   

Here is a copy of my edited 92XXM2-2.INI
file (enables the Levels tab and Automatic Input selection
en/disabling). Alternately, if you are so-inclined, you could open
regedit and
alter these settings manually. However when you do so, the changes get
wiped out by a re-install of the driver, so altering the INI file is
really your best bet.

You
can now uninstall the device you have in device manager and re-install.
Reboot to ensure you apply the change to the Sigmatel chipset.

After
rebooting, plug in your device. A pop-up should prompt you for the
input type. You may choose to tell it to no longer prompt you for this
change. Then, go into the Volume Control, uncheck mute on Input
Monitor,
got to Options, Properties, select Line-in and you should hear your
input. Also, you may choose to drop the volume on the Internal Mic down
to 0%. This will help you avoid horrible feedback should you switch to
the internal mic.

If
you don’t have a D820, it possible that your INI file may be different.
To identify what the proper INI file is,  open regedit and search for
this string:
    SigmaTel High Definition Audio CODEC
Look for
the key named "DriverDesc". In this folder/tree you should also see
"IniPath". Open this key and look at the name of the INI file in the
path. This should be the correct INI for your model.

UPDATE 2/11:
If you feel inclined to do so you can change, with a decent amount of
granularity, which options you can see in the Advanced tab. This is
done by flipping individual bits on or off in the Config_Adv registry
setting. Here are the applicable decimal values for each option:

1 Power Management Amplifier Power Mangement
2 Sampling Rate Sampling Rate adjustment
4 SPDIF AC3/PCM en/disable and Rate Adjustment
8 SPDIF Digital Out en/disable and Rate Adjustment

16

SPDIF

Digital Out en/disable 

32

Dolby

Dolby Digital Live en/disable 

64

Noise Suppression

Noise Suppression en/disable 

128

ASIO

Latency/Rate adjustment, ASIO monitor en/disable 

256

Pop-ups

Jack reconfiguration pop-up en/disable

512

HDMI

HDMI output en/disable 

1024

Bass Management

Bass Routing and boost dB adjustment 

2048

Microphone Selection

Automatic Microphone Selection en/disable 

4096

Internal Speakers

Internal Speaker Muting options 

8192

Headphone Configuration

Redirected headphone en/disable 

16384

(Unknown)

 

32768

Multi-Streaming

Multi-stream retasking en/disable 

65536

Speaker Mute Controls

Additional internal speaker muting options 

To enable or disable any of these options, just add or subtract it’s
decimal value (shown) from the decimal value you see in regedit (when
the decimal radio is selected). For example, to display configuration
options for Pop-ups, Microphone Selection, and Noise Suppression, just
add 256+2048+64. This gives you 2368, which you can paste into regedit
when you select the decimal radio. This will convert to 940 in hex.