Raymond Yau wrote:

Did you use mono or stereo in playback and capture?

mono

Did your capture volume /boost set to 0dB?

yes

Do your sound card support the sampling rate ?

Yes

Refer to the datasheet and your alsamixertest result , the card seem not has fixed gain for each step

http://www.steila.com/USB4IO/CMedia/CM119.pdf Card is using C-Media CM119. Datasheet seems to show 38 volume control steps? Should the steps be 38 instead of 151? Or are these values unrelated?

Are you using version 48.11?

Yes