In the world of high-performance bass amps, Ampeg's SVT amplifiers are in a class by themselves. In true Ampeg tradition, the SVT-4 PRO offers you more power, performance and flexibility than any other bass amplifier in its class.SVT-4PRO offers an expansive palette of tonal options. The Frequency control allows you to select the center frequency for the Midrange control, giving you five distinct voicing options for the Midrange.