I can only comment for my own (genuine) SB16.

I invoked the suite of programs that came with the card and selected
"Creative Mixer".

By clicking on the icon at the top left of the window you obtain a menu
which includes "Recording Settings". Following this yields the AGC
enable/disable facility. It may be that a given clone will allow an
eqivalent way in, or it may not even have an AGC facility at all. I do not
know the Windows API way of handling this, the Multimedia Reference that
came with my C++ Builder has nothing on it.

Use the AGC facility with care and do not overload the input or you get
terrible effects. It is a pity that soundcards do not limit in the way that
op-amps do.

73
Lionel
G3PPT