Abstract: An audio frequency filter for a mixing console equalizer typically has a manual frequency control for setting its operating frequency range, and a manual gain control for controlling the gain of the filter independently of the set frequency range. The present filter further provides gain adjustment means for automatically adjusting the gain of the filter in dependence on the position of said operating frequency range relative to a reference frequency that lies intermediate the lower and upper ends of the audio frequency spectrum, the gain adjustment means being such that the filter gain is greater the further said operating frequency range is moved away from said reference frequency towards a said end of the audio spectrum. As a result, signal frequencies at the extreme of the audio spectrum are automatically boosted.

Abstract: Electrical signal mixing apparatus for recording studio or live performance comprising a plurality of input channels having means for conditioning input signals applied thereto, a plurality of sub-group channels to which the signals from input channels can be selectively assigned, and a pair of output channels which may receive signals directly from the input channels or via the sub-group channels. Routing interconnections between the input, sub-group and output channels are controlled by a microprocessor in dependence on operator selections effected via a single manually operable switch control on each channel. The microprocessor detects destination assignments indicated by operation of the switch on a sub-group or output channel, and act to complete analogue interconnections between input channels and the identified sub-group or output channels upon subsequent actuation of the input channel selector switches.