Here is software and documentation by Taka-san, JI1UDD which allows limiting of both receive and transmit audio via the AK4951 CODEC of the HL2+ Companion Board.
Click on the "Release" folder, then the latest release date folder and download the .zip.
Unzip the .zip file. Double click ak4951_ctrl.exe
Follow instructions found in the formatted/updated Manual
Original manual with added graphics:
Audio Path Diagrams:
