An apparatus for providing a feedback force includes a calculating unit and a force feedback displacement controller. The calculating unit receives relative position information of a first object and a second object and geometric information of the first object and the second object. If the first object and the second object are not in contact, the calculating unit calculates a force feedback value based on the relative position information and the geometric information. The force feedback displacement controller outputs a displacement command, and receives the force feedback value. The displacement command allows the first object to move with respect to the second object. The force feedback displacement controller includes a displacement unit that generates the displacement command based on an operation of a user, and a force feedback unit that provides a feedback force to the displacement unit based on the force feedback value.

A mixer controller includes a housing for audio processing equipment having a device surface and a front edge, and a plurality of audio processing devices mounted on the device surface. The plurality of audio processing devices include at least a first channel and a second channel. The mixer controller includes a cross-fader that controls an amount of audio output from the first channel and output from the second channel by sliding the cross-fader between a first position and a second position. The cross-fader includes an extension, the extension having an end that extends forward of the front edge of the housing.