Can't disable Processing


I’m currently trying to disable the processing of the BC127 with the following command:
HFP_CONFIG=OFF ON OFF OFF ON OFF. This would allow me to use external processing. The problem is that if I send an analog audio stream through the MIC_IN jack of the BC127, which contains background noise or pure white noise, the output of this will be highly noticeable that the signal still went through some processing.
Is there any limitation on the disabling the processing for noise reduction and echo cancelling on the analog path?