Fender Bassman 100T 100-Watt Tube Bass Amp Head OUTPUT POWER selector switch offering: 100W mode (full power), 25W mode (with automatic volume adjustment, identical tone at a lower volume!), SILENT RECORD mode (allows use of the tube power amplifier without speakers connected XLR 'POST' signal is taken from power amp output). FENDER AUTOMATIC BIAS for output tube monitoring/adjusting. Vintage - VOL, BASS (pull DEEP), MID, TREBLE (pull BRIGHT); Overdrive - GAIN, BLEND, VOL, BASS (pull DEEP), MID FREQ, MID LVL, TREBLE (pull BRIGHT); MASTER (pull MUTE)