Audio Control Richter Scale Equalizer

Vintage equalizer Audio Control Richter Scale. A unique special-purpose five-band graphic equalizer and wave analyser. Operates only at frequencies below about 200 Hz. Its filters, spaced at half-octave intervals, have center frequencies of 31.5, 45, 63, 90, and 125 Hz. Each slider control adjusts the gain in its own frequency band over a ± 12-dB range. Adjusting any graphic equalizer by ear can be difficult, and to simplify the process the RS contains a tunable warble-tone generator covering the range from 31.5 to 250 Hz. Its frequency is adjusted by a small front-panel knob whose calibration points correspond to the filter center frequencies (the 250-Hz point serves as a reference level to which the response at the other frequencies can be matched by use of the slider controls). Creates insane bass for your audio system, like you have never before heard. Quite literally a need in a haystack find.