Enabling Audio Input Monitoring in Windows Vista/7

Now and then I like to plug my MP3 player in to the "Line-In" jack of laptop and play my music through my Laptop speakers. When I was using Windows XP, this was easy. I just plugged it in to the Line-In jack, unmuted the Line-In and away I went.

Control Panel > Sound > Playback > Speakers Properties > Levels tab

Since changing to a Windows Vista and most recently Windows 7 Enterprise, I discovered that the option to unmute the Line-In was no longer available. Microsoft in all their wisdom have switched it off by default for some sounds cards.

The most commonly affected are Sigmatel and SoundMax. Usually found on Dell laptops (like mine.) However do not dispair, there is a quick solution in form of a registry tweak.

Sigmatel

• First load regedit (START - RUN - type regedit - Click OK.)
• Find: HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class\{4D36E96C-E325-11CE-BFC1-08002BE10318}\0000\Settings\filter\SpeakerHp
• Now create a Binary Value called "EnableInputMonitor" and set the Hex value at 01(Add the 01 to the existing 0000 to make it 0000 01)
• Click OK
• Reboot the computer

 SoundMax

• First load regedit (START - RUN - type regedit - Click OK.)
• Find: [HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class\{4D36E96C-E325-11CE-BFC1-08002BE10318}\0000\AD1983
• Now create a Binary Value called "EnableInputMonitor" and set the Hex value at 01 (Add the 01 to the existing 0000 to make it 0000 01)
• Click OK
• Reboot the computer

The Input Monitor should now be available. Just plug in your player, unmute the Line-In and enjoy your tunes.

NOTE: Always Backup the registry before you begin editing.

Further Sources:
http://blogs.msdn.com/
Dell Community
http://cvibes.info/computers/EnableInputMonitor.html#SigmaTel