The PRO series TB-600 combines 600 watts of power with total tonal finesse and versatility to produce thick, natural and balanced bass tone that sits perfectly in the mix onstage and in the studio. Based on the acclaimed TBP-1 tube bass preamp, the key to its sound is the passive tone stack - the backbone of classic Fender guitar and bass amps - in which each control knob setting affects the sound of the other controls, producing big, warm notes. The overdrive section (gain, volume, blend) sits on top of the clean channel, letting you dial in tone from subtle grind to full-on overdrive. Vari-Q™ is a smart semi-parametric EQ with a user-selectable frequency and 15 dB cut/boost. When boosting frequencies, it automatically widens the focus of the Q for a broader, more musical boost. When cutting frequencies, it automatically narrows the focus of the Q for a well-defined cut (notch). Room Balance is a global EQ shift for cabinets/stage response. A clockwise turn cuts low-end frequencies while raising upper frequencies. A counter-clockwise turn boosts low-end frequencies while cutting upper frequencies. This knob doesn’t affect the XLR out, so you can dial in your stage sound while giving the soundman an unaltered signal.