The speaker output (850W at 4Ω, 600W at 8Ω, and 300W at 16Ω) is joined on the bottom row by the MIDI out/thru/in connectors and the TRS jacks for footswitches 1 and 2. The back-panel I/O, also arranged in two rows, includes two sets of L-R line outputs (XLR and TRS jack) with switched ground lift, followed by a headphone output and the TS jacks of the mono effect loop, with its own switched ground-lift. The Custom knob can be programmed to carry out one of a range of functions, and, finally, there’s a cab simulation on/off toggle switch, with associated blue/red bi-colour LED. A rotary Power Amp control governs the chosen power-amp stage’s distortion. You can choose from: Single-Ended (tube Class A) Split Load (tube Class A/B with a split-load ‘concertina’ phase splitter) Push/Pull (tube Class A/B with a long-tailed pair phase splitter) and Solid State (transistor). Next comes a four-position switch that sets the power-amp topology. A Bright/Normal preamp voicing toggle-switch sits between them. The other modifies the overall level of distortion in the selected stages. Adjacent to these is a second pair of controls, the first of which switches in up to five cascading preamp tube stages. The upper row is less familiar territory: the first two knobs are five-position rotary switches, and these select between the five preset banks (Clean, Glassy, Blues, Crunch and Metal), and the five presets within each bank. The single input jack sits on the left of the lower of two rows, and this hosts familiar gain, bass, middle, treble, presence and master controls, as well as a Modern/Vintage voicing switch.

Other than the global output level, the front-panel controls are all programmable. And the result might appeal equally to the incessant tweakers and those who just want to plug and play. Insanely tweakable, and promising the ability to mimic your own amp, could this be the last word in amp modelling?įor any guitarist, there’s a reassuring air of familiarity and class about the Bias Head’s black, grey and silver enclosure, but its front and rear grilles are purely cosmetic - inside lurks a 25-preset, deeply programmable combination of Positive Grid’s highly regarded Bias Amp software, the DSP to run it, and a 600W Class-D power amp.

Bias guitar amp simulator