Abstract: A circuit for use in connection with a stereo audio system to increase the ambience includes a differencing circuit for receiving a left stereo input and a right stereo input. The differencing circuit produces an output signal having a difference of the left stereo input and the right stereo input. A shelf filtering circuit is operably coupled to the differencing circuit to receive the output signal. The shelf filtering circuit has a first passband range of frequencies wherein the output signal is attenuated at a first level and a second passband range of frequencies wherein the output signal is attenuated at a second level. The shelf filtering circuit has a crossover frequency between the first passband range of frequencies and the second passband range of frequencies. A summing circuit operably coupled to the left input and the right input and operably coupled to the shelf filtering circuit receives an output signal from the shelf filtering circuit.