All the way back in the '40s, Fender introduced the Champ amplifier, then known as the Champion 800. After a lengthy series of part swaps and circuit revisions, Fender arrived at the 5F1, otherwise known as the "Tweed Champ," named so because of its unmistakable wrapping.

It featured just one knob--volume--that went to 12 (in your face, Nigel), and if you've ever played one, that's about all it needs. Just that one knob can coax a myriad of tones from the humble circuit, from gently gritty cleans to honking, mid-heavy blown out distortion.

Unlike most amp-in-a-box devices, the Formula 51 features a preamp, a phase inverter and an output transformer to deliver the full touch-sensitive Tweed experience, with a grip of extremely interactive controls. The Sag control loads down the transformer to your taste, giving you some real-deal blown-out leads with the twist of a knob.

The final control is straight out of the vintage amplifier playbook, incorporating the mid scoop control of the Framus Cobra amp. This time-tested mod essentially turns the mid-leaning Tweed profile into the mid-scooped "blackface" sound of later Champs. Run it at 18V for more headroom or stack it with other pedals to really dig into that transformer!