The Pettyjohn PreDrive is a preamp, boost and tone-shaping pedal for guitar or bass, released by Pettyjohn Electronics in 2014 as the company's first pedal1. It is designed to be the always-on, first pedal in a player's chain, preserving and improving the sound of whatever comes after it23. Delicious Audio called it "their first pedal, a true studio army knife for tone shaping and light saturation" and noted it was the company's bigger hit to date4.
Pettyjohn describes the pedal as having three main functions that work together: PreAmp, PreShape and PreBoost2. Premier Guitar's reviewer summed up what a player can expect from it:
"It's helpful to view the PreDrive less as an effect that will radically transform your tone and more as a tool that can shape your tone in very precise, specific ways."5
The design draws on the technology and designs Stephen Pettyjohn used as a recording engineer6, and the pedal is hand made in the USA with premium analog discrete opamp circuitry2.
What the PreDrive does to your tone
The PreDrive is built to sit at the front of the board and stay on. Its preamp section can deliver overdrive, boost and color to suit stage and studio situations5, but its effects lean toward the subtle side: it is a precision tool rather than a radical tone-changer5. Pedal of the Day's reviewer described it as a pedal that "refines and defines your tone," suited to studio and live use3.
The boost function offers up to 11dB of gain, adding body to the sound23. With the boost on, the circuit can be driven into full saturation for natural compression and rich harmonic content, which Pettyjohn describes as reminiscent of a vintage tube amp driven to the edge of overdrive2. Premier Guitar's reviewer also found the boost works well stacked on top of other dirt: "Stacking the PreDrive's boost on top of a distortion or fuzz shifts your output into even higher gear"5.
The pedal also carries a transformer-coupled direct output on a balanced TRS connection, aimed at players running into digital effects, virtual amps, or recording and re-amping in the studio2.
The controls
The control panel is organized around two footswitches and a set of knobs and toggles52:
| Control | What it does |
|---|---|
| Output volume knob | Sets output level5 |
| Drive mix knob | Blends in drive; used with the harmonic drive switch for light grit and body5 |
| Input volume knob | Sets input level5 |
| Boost gain knob (large center knob) | Sets the gain of the boost; the big top hat knob can be adjusted with your foot52 |
| Low cut knob | Wide-range sweepable low cut filter for smooth, transparent tone shaping52 |
| High cut knob | Wide-range sweepable high cut filter for smooth, transparent tone shaping52 |
| Vari-Z toggle | Matches input impedance to different pickup types52 |
| Harmonic drive toggle | Adds midrange and presence; designed to be used with the drive mix knob5 |
| Preamp footswitch | Engages the preamp section52 |
| Boost footswitch | Engages the boost, up to 11dB23 |
The manual offers directions for two starting points: a touch-sensitive overdrive setting and a prescribed preamp setting5.
Vari-Z
The Vari-Z control adjusts input impedance to accommodate different pickup configurations5. Pettyjohn introduced it as a way to match the impedance of different pickup types used in a variety of guitars2. Premier Guitar's reviewer found that engaging the switch drops the input impedance from 1 to .5 megohms5.
Power and connections: 18V DC
The original PreDrive runs on 18V DC power23. On the back panel it carries the input jack, the 18V DC power jack and the output jack, plus an extra buffer output for a tuner and the transformer-coupled direct output on a balanced TRS connection2. Pedal of the Day's review lists the same connections as Input/Output, Tuner In and Direct Out3.
The 18V DC requirement means the original PreDrive cannot run on a standard 9V supply. The later PreDrive Studio changed this with a dual-rail power section offering a 9V to 18V operation range8.
Versions and the PreDrive Studio
The PreDrive was sold in a standard (PCB) version and a hand-wired version3. In 2017 Pettyjohn introduced the PreDrive Studio, which builds on the original PreDrive and Lift pedal offerings as a studio-grade buffer/boost preamp and EQ8. The Studio version differs from the original in several ways:
| PreDrive | PreDrive Studio | |
|---|---|---|
| Circuit | Analog discrete opamp circuitry2 | Two studio-grade 990-style discrete opamps based on the famed John Hardy 990 chip8 |
| Filters | Sweepable high cut and low cut2 | Two fully analog, wide-range, sweepable HP and LP filters8 |
| Power | 18V DC2 | Dual-rail, 9V to 18V operation range8 |
| Made in | USA, hand made2 | Box and circuit handmade in the Pacific Northwest, USA8 |
Pettyjohn described the Studio as "the absolute pinnacle of studio grade guitar pedals" and said there isn't a more detailed or musical buffer/boost preamp or EQ on the market8. The announcement also mentioned an upcoming counterpart called the PreDrive Live8.
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Questions
What does the Pettyjohn PreDrive do?
It is a preamp, boost and tone-shaping pedal designed to be the first, always-on pedal in your chain. Its three main functions, PreAmp, PreShape and PreBoost, work together to preserve and refine your tone, with up to 11dB of boost and a transformer-coupled direct output for recording or running into digital gear.
What voltage does the Pettyjohn PreDrive use?
The original PreDrive runs on 18V DC power. The later PreDrive Studio widened this with a dual-rail power section that accepts anything from 9V to 18V, so it can share a standard 9V supply.
What is the Vari-Z switch on the PreDrive?
Vari-Z is a mini toggle that adjusts the pedal's input impedance to match different pickup types. Premier Guitar's reviewer found that engaging it drops the input impedance from 1 to .5 megohms, which suits certain pickup configurations.
Is the Pettyjohn PreDrive analog?
Yes. It is built with premium analog discrete opamp circuitry and hand made in the USA. The PreDrive Studio version uses two studio-grade 990-style discrete opamps based on the famed John Hardy 990 chip.
Where is the Pettyjohn PreDrive made?
The original PreDrive is hand made in the USA. The PreDrive Studio's box and circuit are handmade in the Pacific Northwest, USA. The design draws on Stephen Pettyjohn's work as a recording engineer.
What is the difference between the PreDrive and the PreDrive Studio?
The PreDrive Studio builds on the original PreDrive and Lift offerings as a studio-grade buffer/boost preamp and EQ, with balanced input and output, two 990-style discrete opamps, sweepable HP and LP filters, and a 9V to 18V dual-rail power section instead of the original's 18V-only supply.
Sources (8)
- PETTYJOHN ELECTRONICS, JHS Pedals
- Pettyjohn Electronics Introduces the PreDrive, Premier Guitar, 2014-06-02
- PettyJohn Electronics PreDrive, Pedal of the Day, 2015-01-22
- Manufacturers Profiles: Pettyjohn Electronics, Delicious Audio, 2016-12-23
- Pettyjohn Electronics PreDrive Review, Premier Guitar, 2014-10-14
- PreDrive3, Pettyjohn Electronics
- Pettyjohn Electronics Introduces the Lift Buffer/Boost, Premier Guitar, 2016-09-07
- Pettyjohn Electronics Introduces the PreDrive Studio, Premier Guitar, 2017-03-08
