Linux/TLV320AIC3101: recording noise while mic not connected?

Tool/software: Linux

Hi Guys,

I'm using tlv320adc3101 with IPNC RDK 3.8 with kernel 2.6.37 i need to decrease noise. here are the values which i'm setting(MIC is in differential mode on MIC1RP and MIC1RM)

amixer cset name='PCM Playback Volume' 100%,100%
amixer sset 'Line DAC' 100%,100%
amixer sset 'Line Line2 Bypass' 0%,0%
amixer sset 'Line PGA Bypass' 0%,0%
amixer sset 'Mono' on

amixer sset 'Mono Line2 Bypass' 0%,0%
amixer sset 'Mono Mixer DACL1' on
amixer sset 'Mono Mixer PGAR Bypass' on

amixer sset 'AGC' on
amixer sset 'HP DAC' 100%,100%

amixer sset 'HP Line2 Bypass' 0%,0%
amixer sset 'HP PGA Bypass' 100%,100%

amixer sset 'HPCOM' off
amixer sset 'HPCOM DAC' 0%,0%
amixer sset 'HPCOM Line2 Bypass' 0%,0%
amixer sset 'HPCOM PGA Bypass' 0%,0%

amixer sset 'Left DAC Mux' 'DAC_L1'

amixer sset 'Left HPCOM Mixer DACL1' off

amixer sset 'Right HP Mixer DACR1' off
amixer sset 'Right HPCOM Mixer DACR1' off
amixer sset 'Right Line Mixer DACR1' off

amixer sset 'Right PGA Mixer Line1R' on
amixer sset 'Right Line1R Mux' 'differential'

amixer cset name='PGA Capture Volume' 50%,50%

regards,

Ganesh