Sony VGN-S380 VAIO User Manual page 191

Why does my computer record only the left-channel audio with a monaural microphone?
You may need to change the audio channel setting.
1.
Click Start and then Control Panel.
The Control Panel window appears.
2.
Click Sounds, Speech, and Audio Devices and then Sounds and Audio Devices.
3.
Click Volume under Sound recording on the Audio tab.
4.
Select Advanced Controls from the Options menu.
The Advanced button appears for Microphone Balance.
5.
Click the Advanced button and select the Mono Mic check box under Other Controls.
This audio channel setting is only applied to sound recording with a microphone.
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