On Thu, May 10, 2012 at 10:45:08AM +0100, Mark Brown wrote:

On Thu, May 10, 2012 at 05:41:15PM +0800, Shawn Guo wrote:

quoted

The "Mic Bias" here is really a SGTL5000 internal supply.

If it is then what's providing the bias to the mic?  It's common for
chips to have a micbias supply which comes out of the chip and is used
by mics, this is my understanding of what this circuit is.

I did not make myself clear, but you made :)  Yes, this is exactly the
thing on my mind, and the circuit will look like:

     STGTL5000        BOARD
		|
      MIC_IN ---+--- JACK
	^	|     ^
	|	|     |
	|	|     |
    MIC_BAIS----+-----/
		|

Isn't you helped me create this understanding? [1]

Regards,
Shawn

[1] http://article.gmane.org/gmane.linux.alsa.devel/96351