The Henretta Engineering Green Zapper Auto Filter is a small, handmade auto filter pedal, an effect type that sweeps a band of frequencies across your signal automatically rather than under your foot like a wah pedal. What sets the Green Zapper apart is that it responds to your picking dynamics: as Pedal of the Day put it, "The Green Zapper is touch-sensitive, so the harder you play, the more effects you get."1
It is also unusually bare-bones. Guitar World's Billy Voight, reviewing the pedal in January 2013, noted that "There are no knobs (more on that in a second) and no battery compartment."2 Both of its controls live inside the enclosure as trimpots, adjusted with the backplate off.
Power and connections
The Green Zapper is powered by what Guitar World described as a 10mA barrel negative tip plug.2 There is no battery option, so an adapter is required from the first plug-in. The power connector and both the input and output jacks are all side mounted, which keeps the pedal's tiny 2" x 2" footprint clear on top.12
With no battery compartment, the Green Zapper cannot run standalone. It needs an adapter supply, and its 10mA draw is light enough for nearly any power supply output.2
Controls
Both controls are internal trimmers rather than foot-accessible knobs. Guitar World explains how to reach them: the backplate is held by four screws, and removing those exposes the two trimpots, Sensitivity and Range.2
| Control | Location | What it does |
|---|---|---|
| Sensitivity | Internal trimmer, under the four-screw backplate | Sets how strongly the pedal responds to your playing dynamics; shipped set for single-coil guitars, dialed back for humbuckers or bass2 |
| Range | Internal trimmer, under the four-screw backplate | Pedal of the Day says it "controls the Range of the effect, or the width of the range of the frequencies being swept"1 |
The pedal ships set up for single-coil guitars, so players with humbuckers, or bassists, will want to turn the Sensitivity trimmer down before judging it.2
Inside the circuit
The Green Zapper uses a TL072 op amp, and Pedal of the Day points out that it is switchable: "You can also switch out the TL072 internal op amp as well, allowing you to experiment and find completely new sounds."1 That makes it an unusual choice for players who like to modify their pedals, since swapping one chip changes the character of the filter.
What reviewers found
Guitar World's reviewer found the pedal's dynamic response to be its defining trait: played softly it was smooth and musical, and the harder the playing got, the fizzier and nastier it got.2
Pedal of the Day's reviewer found it favored fuller playing, working much better for chords as opposed to individual notes, as the dynamics appear much more present when multiple notes are played simultaneously.1
Videos
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Phil Vickman
Tim Calloway
Questions
Does the Henretta Green Zapper take a battery?
No. Guitar World's review notes there is no battery compartment, so the pedal runs only from an external 9-volt DC supply with a barrel negative tip plug. If you plan to put one on a board, budget for a standard 9V adapter output or a spot on an isolated power supply.
Is the Green Zapper true bypass?
Yes. Guitar World's review describes the switch as true bypass, with a bright green LED showing when the pedal is on. That means the pedal's circuit is out of the signal path entirely when it is switched off.
How do you adjust the Green Zapper's sensitivity?
With a screwdriver, not a knob. The Sensitivity control is an internal trimmer, and you reach it by removing the four backplate screws. Guitar World notes the pedal ships set for single-coil guitars, and that you dial the trimmer back for humbuckers or bass.
How much current does the Green Zapper draw?
Guitar World's review gives a draw of 10mA at 9 volts, which is light enough for almost any pedalboard power supply output.
Is the Green Zapper set for single-coil or humbucker guitars?
As shipped it is set for single-coil guitars, according to Guitar World's review. The internal Sensitivity trimmer is adjusted by removing the four backplate screws, and the same review says you dial it back for humbucker-equipped guitars or bass.
Sources (2)
- Henretta Engineering Green Zapper Auto Filter, Pedal of the Day, 2015-01-31
- Review: Henretta Engineering's Tiny Green Zapper Auto Filter Pedal, Guitar World, 2013-01-16