The Sonic Maximizer is a dual channel enhancer designed to operate with -10dBu levels. It works by applying phase correction to the high frequencies which it does by splitting the sound into 3 bands, crossover frequencies being 150Hz and 1200Hz, and applying delays to the two lower bands. The high band passes through a VCA and is controlled in relation to the mid band. There are two modes - 'Auto' mode provides dynamic response so that the 422A expands or compresses the high band in relation to the mid, while in 'Manual' a factory preset expansion ratio is applied. Each channel has a Lo-contour and a Definition knob. Lo-contour is for bass EQ at 50Hz, Definition regulates the processing of the high band in relation to the mid and effectively adds more top end.