Benson Amps Preamp Pedal

The Benson Amps Preamp Pedal is an amp-in-a-box preamp pedal that packs the front end of the maker's Chimera 30 watt guitar amplifier into a stompbox. Benson describes the result as "an extremely amp-like and versatile clean boost/overdrive/fuzz pedal that imparts rich harmonics and a very musical EQ to your signal chain, truly a Chimera in a box"¹. In other words, it is one pedal that can serve as a clean boost, a low-to-medium overdrive, or push into fuzz, depending on where the Gain knob sits.

Benson Amps launched the Preamp as its first pedal in May 2018, at a list price of $249²¹. It remains in the maker's lineup at $249.00 as of the current product page¹.

An amp-style preamp in a pedal

The idea behind the pedal is simple: take the preamp circuit of a tube amp a player already likes and put it on a pedalboard. The circuit is based on the Benson Chimera 30 watt guitar amplifier, but substitutes FET transistors for the vacuum tubes¹. FETs (field-effect transistors) are chosen for the way their clipping and response characteristics resemble tube triode stages, which is what lets a solid-state pedal behave like an amp's front end.

Guitar.com, covering the 2018 launch, described the design the same way: "Instead of tubes, the Benson Preamp uses FET transistors to yield 'amp-like' boost, overdrive, fuzz, EQ and buffer features"³. The same report noted the pedal "takes all the good stuff from the boutique maker's lauded Chimera tube amp and packs it into a versatile stompbox"³.

On That Pedal Show, Chris Benson explained the pedal's origin in his own words²⁴:

The four controls keep the pedal simple. Guitar.com put it plainly at launch: "You only have four controls to play with: 'Volume,' 'Drive,' 'Bass' and 'Treble'"³. The maker's current page lists them as Gain, Volume, Treble and Bass¹.

Power comes from a 9V DC Boss-style adapter or a battery, with a 50mA current draw¹. That is low enough to run from most isolated pedalboard supplies, and the battery option means the pedal works without any external power at all.

From the Chimera amplifier to FET circuit

The lineage runs directly from the Chimera amp. The maker states the circuit is based on the Chimera 30 watt guitar amplifier, with FET transistors substituted for the vacuum tubes¹. Pedal of the Day, reviewing the related Chase Bliss collaboration, spelled out the topology: "The Benson Preamp circuit comes from their Chimera tube amp, but uses FET transistors in place of the amp's 12AX7's triode stages"⁶. So each 12AX7 triode gain stage in the amp's front end has a corresponding FET stage in the pedal.

That circuit has since traveled beyond the original pedal:

• Benson Germanium Preamp: a variant that replaces the first FET transistor of the Preamp pedal with a germanium gain stage taken from Benson's servo-biased Germanium Boost pedal⁷. Pedal of the Day called it a build on "the first pedal that Benson ever released"⁸, and Delicious Audio reported that "This Germanium version was built on the experience gathered by Chris Benson while working on the Germanium Boost"⁹.
• Chase Bliss Preamp MKII: a collaboration built around the same front-end circuitry of a Chimera tube amp, substituting FET transistors for the 12AX7 triode stages¹⁰.
• PedalPCB Son of Ben: a DIY PCB that builders compare to the Benson Preamp circuit. PedalPCB notes it is not affiliated with Benson Amps¹¹.

The Germanium Preamp is worth knowing about when comparing versions. Benson calls it "an alternate universe take on our flagship pedal that marries the incomparable feel of the germanium with the careful equalization and tone controls of the preamp pedal," and describes the result as "a slightly lower gain, but richer sounding and feeling overdrive/boost/fuzz"⁷. Its Treble control is implemented as a low pass filter⁷. A player who wants the original FET character throughout the circuit stays with the standard Preamp; one who wants a germanium first stage and a softer ceiling on gain has the variant.

For a sense of how the maker himself frames the pedal, this That Pedal Show conversation with Chris Benson covers the Preamp's move from his amplifiers into FET-based pedal form:

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