Anchor Drive MOSFET Overdrive Pedal Hand Wired Tagboard Circuit

Description

The Anchor Drive is a dual stage MOSFET overdrive built as a small preamp rather than a typical clipping pedal.
Inside the enclosure are two cascaded MOSFET gain stages using BS170 or 2N7000 devices. Each stage has its own level control so the relationship between the stages can be adjusted rather than fixed. This mirrors the way amplifier gain stages interact.
The circuit is assembled on traditional tagboard using through hole components selected during the build. The layout remains visible and serviceable in the same way early amplifier circuits were constructed.
Three controls shape the behaviour of the circuit.
Preamp sets the level of the first MOSFET stage and determines how strongly the second stage is driven.
Power Amp controls the gain of the second stage where most of the saturation occurs.
Master Volume sets the final output level and allows the pedal to be used as either a gain stage or a clean level boost.
Power is supplied by a standard 9V centre negative supply and current draw is low enough to sit comfortably on most pedalboards.
Each Anchor Drive is assembled individually and the exact component selection may vary slightly from build to build as part of the workshop process.
Description of Sound
At lower settings the Anchor Drive behaves as a clean tone shaper. The first MOSFET stage remains mostly linear and the pedal adds presence and body without obvious distortion.
As the Preamp control is increased the second stage begins to saturate. This produces the mid focused overdrive associated with seventies British amplifier tones. Notes remain articulate and the circuit responds closely to picking dynamics.
Driving both stages harder moves the pedal into heavier territory. The interaction between the MOSFET stages produces dense harmonics and compression that resembles a small amplifier being pushed beyond its comfortable range.
At extreme settings the circuit can approach a ragged almost fuzz like character where sustain increases and the edges of notes become less controlled.
The Anchor Drive cleans up well from the guitar volume control and can move from driven rhythm to cleaner tones without touching the pedal itself.

This is a one off hand built pedal assembled in the workshop using traditional construction methods. The circuit and appearance may not be repeated in exactly the same form again.
If the idea of a MOSFET driven amplifier style gain stage appeals to you, this one is available.