The GFI System Jonassus is a dual-channel analog overdrive pedal from Indonesian manufacturer GFI System. It puts two drives in one box: what the maker calls a "sweet, warm, and articulate low-gain overdrive" on the Low Channel, and a "thick and ballsy medium-high gain overdrive" on the High Channel1. Each channel has its own Volume, Gain and Clipping control set, and a single shared tone knob shapes both2.
The pedal was announced in July 2018, when most major pedal videographers unveiled demo videos of it on the same day2. Guitar World's Paul Riario reviewed it and found it to be:
"the kind of touch-sensitive overdrive with a sweetly refined saturation and warm grind"3
Two overdrives in one pedal
The Jonassus is built around two separate overdrive channels. The Low Channel handles the low-gain end, the territory of edge-of-breakup grit and light push, while the High Channel covers medium-high gain for thicker, more saturated leads and rhythms1. Guitar World described it as a touch-sensitive overdrive, meaning the sound cleans up and drives up in response to how hard you pick3.
Each channel has its own Volume, Gain and Clipping controls, so you can dial in two very different drive sounds and jump between them with a footswitch1. The tone knob is shared between the two channels, which is worth knowing before you buy: a setting that flatters the low-gain channel will also be applied when you switch to the high-gain side2.
Controls and footswitches
The pedal carries two footswitches, which Guitar World called "two rugged footswitches" governing on/off and channel select3.
| Control | What it does |
|---|---|
| Left footswitch | Bypasses or engages the pedal1 |
| Right footswitch | Selects which Volume/Gain/Clipping (V.G.C) control set is active, the left-side or the right-side1 |
| Clipping Mode | Chooses among three clipping settings, assignable per channel13 |
| Tone | Shared between both channels2 |
Because the right footswitch selects one control set at a time, the two channels alternate rather than stack: you get one drive sound at a time, chosen by which V.G.C. set is active1.
Three clipping modes
The Clipping control offers three settings, each giving the drive a different character1:
- Diode / Asymmetric: more compression and bite1
- Diode / Symmetric: less compression, smooth and balanced1
- LED / Symmetric: wide open and warm1
Guitar World noted that the three clipping stages, accessed via the clipping button, can be assigned to either channel, so each of your two sounds can use a different clipping character. The reviewer described the symmetric diode clipping stage, indicated by a green LED, as sounding less compressed with a silkier drive tone3.
Power and connections
The Jonassus runs on a standard 9V DC supply with a negative center plug, drawing about 40 mA1. That current draw is low enough that it can share an isolated output or a daisy chain with other compact analog pedals without straining a typical power supply.
At 12 x 7.7 x 5.5 cm and 0.6 kg, it sits in the same size class as most compact dual-drive pedals1.
What reviewers said
Guitar World's Paul Riario reviewed the Jonassus Drive and praised its touch sensitivity, describing "sweetly refined saturation and warm grind"3. His one reservation was about value rather than sound:
"There are more competitively priced overdrive pedals on the market."3
Paul Riario, Guitar World3
Delicious Audio, covering the announcement in 2018, highlighted the dual-channel analog design with its three clipping modes and shared tone knob as the pedal's defining features2.
Videos
Andertons Music Co
Premier Guitar
GFI System
Questions
Can the GFI System Jonassus run both channels at once?
No. The right footswitch selects which Volume/Gain/Clipping control set is active, the left-side set or the right-side set, so you switch between the two channels rather than stacking them. The left footswitch turns the pedal on and off.
Is the GFI System Jonassus analog?
Yes. It is described as a dual-channel low gain and high gain analog overdrive with three clipping modes, and it was announced that way when it launched in July 2018.
Does the Jonassus have a separate tone knob for each channel?
No. The two channels share a single tone knob, while each channel has its own Volume, Gain and Clipping control set that the right footswitch selects between.
How much does the GFI System Jonassus weigh?
It weighs 0.6 kg, about 1.2 lbs, and measures 12 cm long by 7.7 cm wide by 5.5 cm high, which keeps it in standard compact pedalboard territory.
Sources (3)
- Jonassus, GFI System
- GFI System Jonassus Dual Channel Overdrive, Delicious Audio, 2018-07-10
- GFI System Jonassus Drive review, Guitar World, 2020-04-09
