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Pettyjohn Electronics PreDrive Review

A high-end preamp that delivers surgically precise tone-shaping power.

Pettyjohn Electronics PreDrive is essentially a highly tailorable preamp in a stompbox format—a cool vehicle for a player that doesn’t like a ton of pedals. It’s designed to be the first pedal in your chain and the kind of pedal that you never turn off. For players that rarely dabble in high-gain tones it might be the only pedal they ever really need. As the plentitude of knobs suggests, this preamp can deliver overdrive, boost, and color to suit countless stage and studio situations.

Big, Burly Control Freak
The PreDrive’s relic’d enclosure is bigger and more tank-like than an average stompbox. The pedal’s extra size is not wasted, however. The three knobs along the top are for output volume, drive mix, and input volume. The center knob, which is significantly larger than the other knobs, controls boost gain, and there are two smaller knobs for low cut and high cut. Two mini toggle switches are for the mysteriously named—but powerful—Vari-Z and harmonic drive functions. At the bottom of the control panel are two footswitches for engaging the preamp and boost. The ins and outs on the top corner of the pedal comprise three outputs—output, direct out, and buffered tuner out—and a single input.

Previewing the PreDrive
To test the PreDrive I used an Ernie Ball/Music Man Axis Sport and a Mesa/Boogie Mark IV. I also checked out its compatibility with pedals including a Hermida Audio Zendrive and an MI Audio Tube Zone.

The PreDrive can do remarkable things in the simplest applications. My Mark IV sounds pretty great clean, but by engaging the preamp using a setting prescribed in the PreDrive’s user manual, I heard much greater detail, especially playing fuller, more harmonically intricate chord voicings. From this test alone, it’s easy to see why Pettyjohn touts the PreDrive’s potential to be an “always-on” pedal. It’s like having an engineer at a mixing desk candy coating your tone.

Even at the highest boost levels, the PreDrive is among the most transparent boosts I have come across.

With a really lovely fundamental clean sound in place, I engaged the boost function and ran it through its full range, which maxes out at a considerable 11 dB of clean boost. Even at the highest boost levels, the PreDrive is among the most transparent boosts I have come across. It adds very little coloration to your tone. And thanks to the boost knob’s large size, the boost level can be fine tuned on the fly very easily.

More Tone Tweaks
The PreDrive’s sweepable EQ section has a broad spectrum. The tone shaping capabilities of the low- and high-cut controls alone is impressive and can help you coax new sounds out of an instrument that might otherwise lack versatility. The low-cut knob has a range from 20 Hz to 1 kHz, and the high-cut knob has a range from 20 kHz down to 1 kHz. Adjusting these knobs I was able to go from a sharp, bright attack for funk or Americana-styled open-chord strumming to a warmer, more muted tone for jazzy chord melodies.

More tone-shaping possibilities are available via the pedal’s two mini-toggle switches. The harmonic drive switch adds midrange and presence and is designed to be used in conjunction with the drive mix knob to add light grit and body. The Vari-Z control adjusts input impedance to accommodate different pickup configurations. Engaging this switch drops the input impedance from 1 to .5?, which can soften single-coil output that sounds too harsh and brittle.


Can really help fine-tune your tone. Great for mystery backlines and studio work alike.

Pricey. Can take some time to tweak.


Ease of Use:



$599 (as tested, $399 PCB version also available)

Pettyjohn PreDrive

Pushing the PreDrive
The manual offers directions for a touch-sensitive overdrive setting. When I dialed it up I got a killer low-gain sound that’s a dead ringer for a vintage amp cranked to 10. The output takes on a raucous edge that’s perfect for rootsy and rocking rhythm parts. As advertised, it feels very dynamic, and puts overdrive shades from dirty to near clean at your disposal depending on your attack. I loved the considerable tone contrast between strumming open chords with a heavy hand and softly picking arpeggios.

Because the PreDrive is really a tone shaping preamp rather than an overdrive, to get searing leads (especially with low gain amps) you’ll want to add in a dirt box. And you can get absolutely killer lead and rhythm tones using the PreDrive to massage your output before it hits the dirt pedal and sculpt the tone of the dirt box itself. Stacking the PreDrive’s boost on top of a distortion or fuzz shifts your output into even higher gear.

The Verdict
As versatile as it is, the PreDrive’s effects are on the subtler side. It’s an adult effect, if you will, that will reward a discriminating ear more than a player looking to tear the roof off. 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. It helps get the best representation of your guitar’s sound through your effects and amp. It can also be a recording engineer’s dream, and the transformer-coupled direct out also allows you to record the guitar tone on a second channel so you can reamp the guitar sound, or mix it with an effects-colored tone from the guitar going through the normal output.

At $599, the PreDrive costs a considerable chunk of change, but it’s beautifully made and built with components more common in high-end microphones and outboard studio signal processing gear (and you can also opt for the PCB-wired, $399 version.) If you are looking to maximize the sonic potential of your existing gear both onstage and in the studio, the Pettyjohn PreDrive might be the answer. And while it costs a pretty penny, the splurge can take your tone a long, long way.