The GFI System Jonassus Drive is a dual-channel overdrive pedal: a low-gain channel on one side and a medium to higher-gain channel on the other, in one stompbox1. GFI System describes the Low Channel as a sweet, warm and articulate low-gain overdrive and the High Channel as a thick, ballsy medium-high gain overdrive2. Guitar World's reviewer, Paul Riario, called it "the kind of touch-sensitive overdrive with a sweetly refined saturation and warm grind"1.
The pedal is a dual-channel stompbox, with a low-gain channel on one side and a medium to higher-gain channel on the other12.
Two channels, one pedal
The Jonassus puts two drive voices in a single enclosure. Each channel has its own volume and gain controls, with a shared tone control1. GFI System's product page describes the pairing as a sweet, warm and articulate low-gain overdrive (Low Channel) plus a thick and ballsy medium-high gain overdrive (High Channel)2.
For a player, that means one pedal can cover both a light edge for rhythm work and a heavier voice for leads, without stacking two separate overdrives. Guitar World's reviewer found the pedal "carves out a niche unfilled by previous drive pedals," crediting its abundant controls and dynamic LED clipping for rhythm and lead playing1.
Controls and footswitches
Two rugged footswitches govern on/off and channel select1.
| Control | What it does |
|---|---|
| Left footswitch | Bypasses/engages the pedal2 |
| Right footswitch | Selects which Volume/Gain/Clipping (V.G.C) control set is activated, the left-side or the right-side2 |
| Volume (per channel) | Sets the output level of the active channel2 |
| Gain (per channel) | Sets the drive amount of the active channel2 |
| Clipping (per channel) | Selects the clipping mode for the active channel2 |
| Tone (shared) | Shapes the overall frequency balance of both channels1 |
The right footswitch is the heart of the dual-channel design: it flips between the two Volume/Gain/Clipping control sets, so you can set up two completely different drive sounds and switch between them with one press2.
Clipping options and DIP switch configurations
Each drive channel has three selectable clipping options, set by DIP switches inside the pedal3. Guitar World notes the DIP switches allow you to set up the pedal in three dual-channel configurations1.
| Clipping Mode | Character |
|---|---|
| Diode / Asymmetric | More compression and bite2 |
| Diode / Symmetric | Symmetric diode clipping2 |
| LED / Symmetric | Wide opened, warm2 |
The clipping mode is shown by an LED indicator. Guitar World's review describes asymmetric diode clipping as indicated by blue, with a more compressed and crisp gain character1.
"Diode / Asymmetric - more compression and bites."
For players comparing drive types, the Jonassus sits in the overdrive family rather than distortion or fuzz: its gain range runs from low gain on one channel to medium-high gain on the other1.
Power and connectivity
The pedal requires a 9VDC power adapter with a negative center2, the same standard supply used by most compact pedals. It is true bypass1, so the signal passes through unprocessed when the pedal is off.
The Jonassus needs a 9VDC negative-center supply2. There is no battery option in the published specifications, so plan on a pedalboard power supply or a dedicated adapter.
What reviewers said
Guitar World's Paul Riario reviewed the Jonassus and summarized it as a touch-sensitive overdrive with sweetly refined saturation and warm grind1. His overall verdict was that the pedal "carves out a niche unfilled by previous drive pedals," pointing to its array of features including LED clipping, independent controls for each of its two channels and clickless footswitches1.
Delicious Audio's Paolo De Gregorio covered the 2018 announcement, noting that each drive has three selectable clipping options3.
Videos
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GFI System
Questions
Is the GFI System Jonassus true bypass?
Yes. Guitar World's review lists the Jonassus as true bypass, so with the pedal disengaged your signal passes through without buffering. Engaging the left footswitch turns the overdrive on.
What power supply does the Jonassus Drive need?
It runs on a 9V DC power adapter with a negative center, the same standard supply as most compact pedals. GFI System lists the power source requirement as 9VDC, negative center.
How much does the GFI System Jonassus cost?
GFI System lists the Jonassus at USD 239.00 on its product page. Guitar World's review gives a $249 street price, so the two published figures differ slightly depending on where you look.
What do the LED colors on the Jonassus mean?
The clipping mode indicator shows which clipping circuit is active. Blue indicates asymmetric diode clipping, which Guitar World's reviewer described as a more compressed and crisp gain character.
Sources (3)
- GFI System Jonassus Drive review, Guitar World, 2020-04-09
- Jonassus, GFI System
- GFI System Jonassus Dual Channel Overdrive, Delicious Audio, 2018-07-10
