mic input instead of line input in beaglebone audio cape

Hello,

I need to use microphone on beaglebone audio cap. I powered up VBias voltage on Page0/Register 25: MICBIAS Control Register. I think there is a opamp(preamplifier) for MIC input(simplified block diagram at page 3, in user manual of TLV320AIC3106). But I couldn't find any register for using this preamplifier for MIC inputs instead of LINE.

Thanks.

Mehmet Kurnaz