The Catalinbread Formula No. 5 is an overdrive pedal from Catalinbread that models the preamp and tone stack of a small 1950s tweed amp, the kind Catalinbread points to as the Fender Harvard 5F1012. Rather than a generic drive circuit, it aims to behave like the front end of one of those old amps, right down to the quirks: the tone control loses its effect as the gain goes up, and the pedal never really gets fully clean even with the gain rolled back1.
Pedal of the Day's reviewer described the result as a "powerful but somewhat soothing tone," with an earthly, smooth drive reminiscent of classic rock riffs and a golden vintage amp sound3.
A tweed amp in a pedal
Catalinbread built the Formula No. 5 around the circuit behavior of old amps like the Harvard 5F10, a small tweed combo with a single-knob tone control and a second gain stage that saturates as you push it1. The pedal copies that structure: the Gain control saturates the second stage at a varying level, emphasizing the frequency dialed in with the Tone knob, and it never really makes the sound clean even when rolled all the way back, just like the real amp5.
Aion FX, whose Asteria project replicates the circuit, notes that the Formula No. 5 blurs the line between a preamp and an overdrive. Like a true preamp, it is very reactive to what comes before it, so Aion FX suggests placing it after other drive pedals but before modulation, though it also works as a standalone overdrive6. The original version also replicates the quirks of the old Deluxe-style amps, including a tone control whose effect diminishes as gain is turned up, with almost no change across the sweep at maximum drive6.
For players comparing it with other Catalinbread amp-in-a-box pedals, the company later expanded the tweed idea into the Formula No. 55, which gearnews described as seeking to squeeze "that 1950s vintage tweed 100-watt amp tone into a small, neat, modern effects pedal, just with lots" of vintage drive2.
The controls
The Formula No. 5 keeps the three-knob layout of the amps it copies. Catalinbread's own descriptions of each control51:
| Control | What it does |
|---|---|
| VOL | More makes the pedal loud. Less makes the pedal quiet.5 |
| TONE | Modeled after the single-knob tone control in old amps such as the Harvard 5F10. It adjusts a gentle low-pass filter with a subtle mid scoop, tied directly to the Gain control, so you can push those frequencies harder as gain increases.5 |
| GAIN | Saturates the second stage at a varying level that emphasizes the frequency set by the Tone knob. Never really makes the sound clean, even rolled all the way back, just like the real amp.5 |
Pedal of the Day's reviewer found the Gain knob rewarding at both ends: with it up to the max, the pedal "can really make it sing," while rolling back the guitar's volume knob yields sparkling cleans3.
Power: 9V to 18V, center-negative
Catalinbread states that the Formula 5 accepts anything between 9V and 18V with a center-negative DC power supply1. The original also ran on a battery, with a reported draw of only 2 mA3.
Plugging in anything other than a 9V to 18V center-negative DC supply, such as a center-positive, AC, or higher-voltage adapter, carries a good chance of damaging the Formula 5 and voiding your warranty, according to Catalinbread1.
History and versions
The Formula No. 5 went through two versions. Aion FX, which replicated both circuits as separate projects, dates the update to 2011 and describes the two versions as similar but different enough to warrant separate builds: the original became the Asteria Mk. I and the second version the Asteria Mk. II6. Both versions used 2N5457 JFETs, which are no longer available in through-hole format7.
Catalinbread currently lists a reissue of the Formula No. 5, with the same control set, the same 9V to 18V center-negative power requirement, and the same warning about voiding the warranty with the wrong adapter5.
The tweed concept continued in the family. The Formula 5F6 followed, and in 2017 Catalinbread added the Formula No. 55, part of the company's Foundation Overdrive series, available from the end of January 2017 with a four-knob layout of Master, Presence, Tone and Volume28.
What reviewers said
Pedal of the Day reviewed the Formula No. 5 twice. In 2014, Mike B praised its powerful but soothing tone and smooth, classic-rock drive character3. Later that year the same reviewer summed up its staying power:
"it hasn't left my board in years, and I can always find a use for it somewhere in my playing, regardless of style or volume."9
Pedal of the Day, 20149
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Questions
Does the Formula No. 5 run on a battery?
Yes. Pedal of the Day's 2014 review listed battery operation alongside 9V to 18V negative-tip DC power, and the pedal draws only 2 mA, so a battery lasts a long time3.
Can I run the Catalinbread Formula No. 5 at 18 volts?
Yes. Catalinbread states the Formula 5 accepts anything between 9V and 18V with a center-negative DC power supply1.
Where is the Formula No. 5 made?
The Formula No. 5 was handbuilt in Portland, Oregon, according to Pedal of the Day's 2014 review3.
Will the wrong power supply void the Catalinbread warranty?
Yes. Catalinbread warns that using anything other than the specified supply risks damaging the pedal and voiding the warranty1.
Sources (9)
- Formula No. 5 (Spaceship Art), Catalinbread Effects
- NAMM 2017: Catalinbread Formula No. 55 Overdrive pedal offers some heavy tweed, gearnews.com, 2017-01-18
- Catalinbread Formula No. 5, Pedal of the Day (www.pedal-of-the-day.com), 2014-05-05
- Catalinbread Formula No. 5 Overdrive, Pedal of the Day, 2014-04-16
- Formula No. 5 (Reissue), Catalinbread Effects
- Asteria Preamp Drive Mk. I, Aion FX, 2020-11-23
- Asteria Preamp Drive Mk. II, Aion FX, 2020-11-23
- Catalinbread Formula No. 55 Overdrive, Delicious Audio, 2017-02-08
- Catalinbread Formula 5F6 Overdrive, Pedal of the Day, 2014-12-17
