Check the listing for details. Fredenstein F603B 500 Series Equalizer. Condition: New. Listed at 517.00 USD. Workhorse 500 Series 4-band EQ The Fredenstein F603B is a high-performance, low-Q 4-band 500 Series inductor EQ that features passive resonant filters and a short, purist signal path for a silky, yet highly detailed sound. The low- and high-frequency filters are shelving types, while the mids are peaking. The shelving filters each have four selectable frequency centers; the bandpass filters offer six. Mini switches let you toggle up or down to your desired filter range, which is indicated by an LED. Each filter offers a +/-16dB gain range. The F603B's high-power output stage has an impedance of less than 20 ohms and can comfortably drive up to +/- 200mA, ensuring no performance hit with even the most complex, demanding loads. A true hard bypass facilitates instant wet/dry comparisons.