The Catalinbread Formula 51 is a new addition to the Portland company’s family of Tweed-style amp-in-a-box pedals, already comprising the Formula 5F6, voiced after a ’57 Deluxe, and the Formula 55, inspired by the preamp section of the Tweed Deluxe. The 51 recreates the tone of a Tweed Champ, a one-knob, 4-watt combo “rehearsal” amp released way back in 1948, which is the predecessor of the Fender Blackface.
The Catalinbread’s box version of this small but raunchy amp expands on the tonal palette of the original, providing two gain knobs (Gain and Volume), a peculiar Tone control and also a Sag knob, which, to quote the builder, “loads down the transformer to your taste, giving you some real-deal blown-out leads with the twist of a knob.”
To get the original amp’s tone and dynamics right, the Catalinbread team has built a circuit featuring a preamp, a discrete power amp simulator and an output transformer, adding the option of 18v compatibility for extra headroom.
The Tone knob emulates a popular mod applied to the Champ, consisting in incorporating the mid scoop control of the Framus Cobra amp, which allows to scoop the mids to achieve a tonal response closer to the one of the Fender Blackface.
Check out the video of the Catalinbread Formula 51, we added it to our article about the best Tweed-style overdrive pedals.
Catalinbread Formula ’51, Builder’s Notes
Homage to the Tweed Champ w/ Variac.
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 discrete power amp simulator 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 Tone 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!