The upgraded Microtubes B7K Ultra features all the versatility and sonic possibilities of the first version plus: (1) Single user loadable cabinet simulation impulse response. (2) Micro-USB B port to connect to PC/Mac to load a different Virtual Cabinet through the Darkglass Suite. (3) 3.5mm headphone output with cabinet simulation. (4) Balanced XLR output with switchable cabinet simulation. Whereas the Level Knob controls the output of the overdrive section the Master volume adjusts the overall volume of the unit. Ideal for fine tuning the output on clean mode. It also serves as a DI level control. Mixes the clean input signal with the overdriven signal. The clean signal remains at unity gain while the volume of the overdriven signal is set by the Level knob, allowing for fine control of the blend ratio. Attack switch sets the amount of treble content to saturate: The "Boost" setting emphasizes the treble content extra clarity and presence. The "Flat" position leaves this register untouched while the "Cut" position will reduce the amount of high frequencies being saturated. Grunt switch sets the amount of low frequency content to saturate by selecting between three different bass boost levels before the clipping stage. B7K Ultra has an internal stereo headphone amplifier capable of driving a minimum load of 16 ohms from the 3.5mm stereo jack. Use the Master volume control to adjust the level. Toggle the cabinet simulation on/off on the Direct Output. This switch completely bypasses all digital circuits and allows you to get a zero latency signal when needed. A Micro USB B connector allows you to connect the pedal to PC/Mac to load cabinet simulation impulse responses to the pedal and control various other settings.