Look at your audio mixer's settings. Under Options you will find Recording Settings. This is where you adjust the input sensitivity of the audio input jack(s). Adjust as appropriate to your desired audio and verify with a free program like "Digital Level Meter" by Paul Marshall from the UK.
Bob Peloquin - KB1VUA
Uniden HomePatrol-1, BC100XLT,
R/S PRO-30, Pro-106, Pro-163 (feed provider)