The JAM Pedals Rattler Bass is a bass distortion pedal from Jam Pedals, the Athens, Greece maker of analog, handmade, hand-painted effects. JAM describes it as delivering "fat, creamy bass distortion with the headroom, articulation and low-end authority modern players need"1. The circuit follows the company's Rattler distortion, itself a take on the ProCo Rat, but is voiced and feature-set for bass: a Mix control blends your clean signal back in so the low end survives at heavy gain, and a second footswitch kicks in a higher-gain stage on demand1.
The current version is the mk.2, released alongside the Rattler MkII in July 2024. Gearnews described the Bass Rattler MKII as "a flexible tool for adding distortion to lower frequencies," priced at $209.00 at launch (also listed at £194.00 / 229.00€, and $222.00 / £199.00 / 239.00€ at a Thomann affiliate listing)2. JAM's own product page lists a regular price of £219.00, tax included1.
A RAT-style distortion for bass
The Rattler Bass belongs to the RAT-style family of distortions. JAM says the pedal is "inspired by the sound of the late '80s ProCo RAT" and delivers "a rich, full-bodied distortion that works equally well for smooth sustain or aggressive grit"3. The original guitar Rattler earned its reputation on that lineage: Delicious Audio included it in its list of the best RAT-style distortions, and later added the Rattler Mk.2 to its in-depth article on the best RAT pedals and clones4.
What separates the bass version is how it handles the low end. JAM says the company "created the Rattler Bass to capture the character and response of our original Rattler distortion, adjusted to preserve" the fundamentals a bassist needs3. The Mix control is the main tool for that: it "sets the ratio of clean and distorted signals, retaining low-end impact and note definition at heavier gain settings," letting you run anything from full distortion to parallel grit with your dry signal underneath1.
The controls and the high-gain footswitch
The Rattler Bass has four knobs and two footswitches1.
| Control | What it does |
|---|---|
| Level | Sets the output volume1 |
| Gain | Controls saturation1 |
| Tone | Shapes the frequency response1 |
| Mix | Blends clean and distorted signals, from full distortion to parallel grit1 |
The right footswitch is the bypass; the left one is the extra. JAM says "the left footswitch activates a higher-gain stage for instant bursts of added saturation"1, which Gearnews summed up as engaging "a higher gain stage for quick moments of heavy saturation"156. The maker positions it for heavier sections and lead moments6.
The pedal also remembers how you left it. Effect and high-gain startup states can be saved independently: you reconnect power while holding the corresponding footswitch, and the pedal comes up in that state next time6. Switching is clickless, which JAM calls out as part of making the pedal stage-friendly6.
Power and connections
The Rattler Bass runs on 9V DC with a center-negative plug, drawing 40 mA1. There is no battery option listed for the mk.2 bass version, unlike the earlier Rattler ltd, which took a 9V battery or 9V DC center-negative7. Input impedance is 500 kΩ and output impedance is under 10 kΩ1, figures that sit comfortably in a normal pedalboard chain. The pedal measures 7.5 x 12 x 5.6 cm (2.9 x 4.7 x 2.2 in) including jacks and controls and weighs 280 g (0.6 lb)1.
JAM ships to the UK DDP, with 20% UK VAT and all duties included, so there are no extra charges on delivery. The maker also offers a 30-day money-back guarantee1.
History, the mk.2 and artwork versions
The mk.2 keeps the old enclosure. Guitar Pedal X noted the new version "externally looks exactly the same as its predecessor" but "has a number of internal circuit changes - including that new proprietary custom OpAmp chip!"8. JAM says its custom discrete-component op-amp "preserves the open, dynamic feel of the original LM308-based circuit"1, and MusicRadar echoed the maker's language, saying the design "preserves the open, dynamic, and tube amp feel that made the original Rattler so revered"9. The guitar Rattler MkII also gained switchable asymmetrical/symmetrical clipping and a mid-boost footswitch10111; the bass version instead gets the Mix control and the high-gain footswitch10111.
Artwork versions
Like other JAM pedals, the Rattler Bass comes in hand-painted custom artwork versions. Every limited artwork pedal is a one-of-a-kind hand-painted piece, and the pedal you receive will differ in detail from the photos shown1. JAM's line for these is "same sound, different artwork"6. Current and recent bass variants include:
- JAM Pedals "Relic" Rattler Bass6
- JAM Pedals "Achenbach" Rattler Bass mk.23
- JAM Pedals Rattler Bass B-Stock, with the same specifications as the standard pedal5
The Rattler Bass sits in JAM's bass lineup alongside pedals like the Dyna-ssoR Bass compressor and the Red Muck Bass, and in the broader distortion pedal category it is one of several compact RAT-style options covered by the press4. For more on the whole family, see the Jam Pedals brand page.
Videos
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Questions
Is the JAM Rattler Bass true bypass?
Yes. JAM Pedals lists the Rattler Bass as true bypass, so your clean signal passes through untouched when the effect is off. The same applies to the Relic and B-Stock versions and to the wider Rattler family.
What op-amp does the JAM Rattler Bass use?
It uses a custom discrete-component op-amp developed by JAM Pedals. The maker says this design preserves the open, dynamic feel of the original LM308-based circuit, the chip that powered the classic ProCo Rat and the original Rattler.
What is the input impedance of the JAM Rattler Bass?
The input impedance is 500 kΩ, and the output impedance is under 10 kΩ, according to JAM Pedals' product page. Those figures are typical for a compact analog distortion pedal and work fine with most basses and pedalboard setups.
How is the Rattler Bass different from the original JAM Rattler?
JAM Pedals says the Rattler Bass captures the character and response of the original Rattler distortion but is adjusted to preserve the low end for bass. It adds a Mix control that blends clean and distorted signals, plus a second footswitch that engages a higher-gain stage.
How big is the JAM Rattler Bass?
It measures 7.5 x 12 x 5.6 cm, or 2.9 x 4.7 x 2.2 inches, including jacks and controls, and weighs 280 g (0.6 lb). That is a standard compact-pedal footprint that fits easily on most pedalboards.
Is the Jam Pedals Bass Rattler MKII based on the ProCo Rat?
Yes, in lineage. JAM Pedals says the Rattler Bass is inspired by the sound of the late '80s ProCo RAT, and press coverage of the Rattler MkII describes it as a modern take on the classic Rat distortion, with the original LM308 chip replaced by a proprietary op-amp.
Sources (11)
- Rattler Bass, JAM Pedals (www.jampedals.com)
- Jam Pedals Rattler MKII: The Boutique Classic Just Got An Upgrade!, gearnews.com, 2024-07-19
- “Achenbach” Rattler Bass mk.2, JAM Pedals (jampedals.com)
- Jam Pedals Rattler Mk.2 Distortion, Delicious Audio, 2025-03-17
- Rattler Bass B-Stock, JAM Pedals (jampedals.com)
- “Relic” Rattler Bass, JAM Pedals (www.jampedals.com)
- Rattler ltd, JAM Pedals (www.jampedals.com)
- Guitar Pedal X, Guitar Pedal X, 2024-07-18
- “The snake has shed its old skin to usher in a new era of decadent saturation!”: Jam Pedals has designed its own op-amp for the Rattler MkII, MusicRadar, 2024-07-19
- “A new era of decadent saturation”: Jam Pedals' Rattler MkII looks to elevate the '80s-era distortion pedal favored by Dave Grohl, James Hetfield and David Gilmour to new heights, Guitar World, 2024-07-22
- Guitar Pedal X, Guitar Pedal X, 2024-12-17
Justin Meldal-Johnsen
