Sound Blaster Cards have an on board Mixer for adjusting the five different Input  device Levels.  This Mixer also has an Output stage with control's for Bass, Treble and Master Volume.  Use this Mixer to match the Gain Levels of the Sound Blaster Card with the Input/Output Device. Correct Level matching results in cleaner Recording and Play back, all Values can be stored as default.  For a full listing on the In/Output Mixer functions, refer to the online manual or download it in PDF or HTML formats.