The Sig has a more sophisticated effects loop, with an isolated power supply which decouples it from the main amp, giving the reverb more presence and less loading on the preamp. There is also a pull -bright switch on the effects level control.

The Sig model also has a dual mode power supply, with 35/50 watt settings via the 3 position standby switch.

The real differences lie in construction, layout, parts selection, tonality, vibe, and feel. It takes twice as long to build a Signature amp. It is tweaked every step of the way by Bill. Components are hand chosen from our regular production parts, labeled after testing key operating parameters, and utilized to best advantage at each stage.In addition, some components not used in our other amps are used in the Sig amps.The results are stunning.

However, clips do not do this amp justice. The overtones and depth of this amp must be experienced first hand, as the feel, touch sensitivity, and dynamics are only realized by the player and his guitar. Eddie Berman said it was the best amp he had ever played in his life. I built one for John Mayer, as he has mine right now. I don't get mine back until he is convinced the replacement I sent him is as good!