The SB-166XL uses Auto-limit rising and reversing circuit and processes auto expander/gate, which automatically adjusts expansion according to the program material, thus eliminating the noise floor during quiet sessions or music pauses. The Stereo/Mono operation switch, makes it easy to adjust the unification effects between L/R channels. Input level selection (+4/-10dBu); LED indicator gives true display of the signal level for easy operation and adjustment.