A line-powered module that is selectively operable in one of a plurality of modes of operation based upon the value of a selection signal. The autocorrelation matrix of the observed data is updated by passing block-wise autocorrelation slides through a filter. In particular embodiments, the tuning stages are connected in series and each of the tuning stages includes a resistor connected in parallel to a switch, which can be disengaged to cause the amplifier to set the gain to an adjacent gain level.