The Case Study Effects Aspen One is an overdrive and boost pedal that puts two circuits in one box: the company's Aspen overdrive and a transparent MOSFET boost, in a single true bypass enclosure with relay switching throughout and an all-analog signal path1. It is available in two versions, Silicon and Germanium, which differ in the clipping diodes used on the drive side1.
What it does
The overdrive side is the heart of the pedal. Pedal of the Day says the Aspen reimagines a classic Expandora-style circuit with dramatically improved post-drive volume and a bass knob for dialing in the low end1. The reviewer's take on its range: "From edge-of-breakup to face-melting fuzz, it covers more ground than any single drive on your board"1.
The boost side is a transparent MOSFET boost. "It's clean most of the way, but then starts to clip when cranked, adding another layer to your drive sound," the review notes1.
A bass knob lets you shape the low end of the drive side, something the original Expandora-style circuit did not offer1.
Order Switching
An Order Switching toggle flips the signal chain order inside the pedal: boost into drive, or drive into boost1. That matters because the two arrangements sound different: a boost pushing the overdrive drives it harder, while the overdrive feeding the boost keeps the drive's character and lifts the level.
Silicon and Germanium versions
The Aspen One comes in two versions, named for the clipping diodes on the drive side1.
| Version | Clipping | Character |
|---|---|---|
| Silicon | Same clipping character as the original Aspen | The standard Aspen voicing1 |
| Germanium | Vintage hand-sourced germanium diodes | "Softer clipping, smoothed highs, and something that's genuinely hard to describe until you hear it"1 |
The Germanium version is the one Pedal of the Day reviewed1.
Where the circuit comes from
The Aspen One pairs two circuits in one true bypass enclosure: the Case Study Aspen overdrive on one side and a transparent MOSFET boost on the other1. The maker describes the overdrive side as covering "more ground than any single drive on your board," from edge-of-breakup tones to fuzz, while the boost stays clean most of the way and begins to clip when cranked1.
What reviewers said
Pedal of the Day's reviewer came away convinced: "This is one of those pedals you know is gonna crush from the instant you turn it on"1.
Videos
Kenyon Reed
The Tone Shepherd
Sunday Tone
Sources (1)
- Case Study Effects Aspen One Ge Overdrive & Boost, Pedal of the Day, 2026-07-30
