SAG: Start with the knob all the way down until you find a tone you like, then inch it up until it does things you like. If it starts sounding farty or weird, it's just too much degradation for the signal level to handle. *More on this knob below.
VOLUME: The Formula 51 sounds great when this knob is set at any position other than zero. Try it!
TONE: Some time ago, back when amp geeks had just started to trade information over the Internet, a “mids” control mod began popping up that was pulled from an amp called the Framus Cobra. This control, wired in reverse, essentially scooped out the mids and turned a burly, mids-focused Tweed amp into a more scooped “blackface” model. And so, we have given you this control as a Tone knob. When it’s all the way down, you’re in Tweed town. When it’s maxed, you’ve got a “blackface,” Jack.
GAIN: This knob functions as the “volume” control on the original Tweed Champ; it controls the preamp gain, or how much juice hits the power amp and transformer. When it’s all the way down, you’re treated to the slightly gritty cleans of the original, as you roll it up you get a cranked Tweed and finally some heavy distortion all the way at the end.
* The headroom and functionality of the SAG is built for using 18V, so when you run at 9V it's very sensitive. Useful range of the SAG control is determined by the signal strength being fed into the Formula 51. Essentially, the SAG knob controls the degradation of the transformer. There are some conditions when the transformer being bogged down doesn't sound great, just like a real amp. This gives you the option to run the "amp" full-tilt as you see fit with or without transformer degradation. You can also think of this as "tape degradation" but just for a transformer rather than magnetic tape. It's a seasoning rather than a main ingredient.
I like to start out by setting everything fully counterclockwise except for the Volume, this sets the gain to minimum, with no sagging or mids adjustment.
Ease up the **Gain** control until you find a sound you like (totally OK if you just dime it immediately), then move on to the Tone control. Try matching this to your amp, but don’t go too far at first, this is supposed to be a Tweed amp after all, the mod came much later in the amp’s history.
At this point, begin slowly moving up the Sag control. There’s a lot to be found in the first little bit of this knob when you’re playing it all by itself. Adjust sparingly. You can really get it cranking when running the F51 at up to 18V or when it’s fully integrated into your existing dirt section. If you have an always-on drive pedal, put the F51 right after it to really take advantage of the Sag.
The Formula 51 requires a center-negative DC power supply between 9 and 18 volts that supplies at least 2mA of current. Any more current than that is fine. Don’t give it the wrong polarity, don’t give it anything outside the recommended voltage range and for Pete’s sake don’t give it AC. Not only will you BBQ the pedal’s innards, but you will also void your warranty. We just can’t recommend it.