The JAM Pedals "Popped Art" RetroVibe mk.4 is a limited artwork edition of JAM's Uni-Vibe-style modulation pedal, delivering chorus and vibrato in one all-analog box. A mode toggle selects Chorus, which JAM describes as the classic pulsing phase character, or Vibrato for pitch-focused movement1. The mk.4 generation adds performance features the earlier RetroVibes did not have: tap tempo, a ramping function, and an expression input, which Delicious Audio covered as a significant update to the line2.
JAM Pedals is the maker of the RetroVibe mk.4, a vibe pedal offered in a standard version and a "Popped Art" finish, with the "Camper" version used by Simon McBride of Deep Purple1.
A Uni-Vibe-style chorus and vibrato
The RetroVibe mk.4 is an all-analog Uni-Vibe-style modulation pedal, a circuit family descended from the vintage Shin-ei Uni-Vibe that players associate with the swirling, vocal pulse of late-1960s and 1970s recordings. JAM Pedals says the mk.4 "preserves the soul of the original RetroVibe while making it far more expressive in performance"4.
The single mode toggle is the heart of how it sounds:
| Setting | What it does |
|---|---|
| Chorus | The classic pulsing phase character of the Uni-Vibe sound1 |
| Vibrato | Pitch-focused movement, the warbling pitch-shifted flavor1 |
The LFO sweeps from 0.5 to 9.5 Hz, covering slow, syrupy swirls through fast, choppy wobble1. Delicious Audio describes the mk.4 as adding tap tempo, a ramping function and an expression input over the mk.3, with wider Speed and Depth sweeps2.
Controls, tap tempo and ramping
The mk.4 carries a TAP/RAMP footswitch alongside its main bypass switch. JAM describes how it works567:
- Tap the TAP/RAMP footswitch to set the modulation speed in time with the music567.
- Hold the footswitch to ramp to a second speed8.
- While holding, adjust the Speed knob to set where the ramp lands, and the Depth knob to set how long the ramp takes to travel there5.
A separate TS input also accepts an external tap-tempo switch, so you can tap from anywhere on your board rather than reaching for the pedal itself1. On That Pedal Show, the presenters noted the addition while demoing the pedal:
"Anyway, this one has tap tempo."
Dan and Mick, That Pedal Show9
For continuous foot control, a TRS input accepts a standard passive 10 kΩ expression pedal mapped to the Speed parameter, the classic Uni-Vibe move of riding the speed with your foot like a wah1. See Expression Pedals for more on how these work.
Power and connections
The RetroVibe mk.4 runs on 9V DC with a center-negative plug, drawing up to 120 mA1. That current draw is on the higher side for an analog pedal of this size, so plan an isolated or adequately rated output on your power supply rather than assuming a shared daisy-chain slot will cover it. Input impedance is 67 kΩ and output impedance is under 10 kΩ1.
The 120 mA maximum draw means a typical 100 mA isolated output may not be enough. Check your power supply's per-output rating before wiring it in.
The mk.4 and its hand-painted artwork editions
The Popped Art RetroVibe mk.4 is one of JAM's custom artwork versions of the pedal. JAM Pedals states plainly that these editions are "same sound, different artwork": the circuit, controls and specifications are identical to the standard RetroVibe mk.4, and only the paint job changes156. 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.
The artwork editions of the RetroVibe mk.4 include:
- JAM Pedals "Camper" RetroVibe mk.4
- JAM Pedals "Fishbone" RetroVibe mk.4
- JAM Pedals "Paths" RetroVibe mk.4
- JAM Pedals "Pink Eye" RetroVibe mk.4
- JAM Pedals "Skin" RetroVibe mk.4
Because each is hand-painted, no two Popped Art pedals look alike, which is the whole appeal of the edition: the same Uni-Vibe-style chorus and vibrato circuit in a finish nobody else has1.
Where it sits in the JAM Pedals lineup
The RetroVibe mk.4 is JAM's modulation flagship, and the maker offers it alongside its WaterFall chorus family, including the JAM Pedals WaterFall and its own artwork editions such as the JAM Pedals "Bewitched" WaterFall and JAM Pedals "Stalagmite Prince" WaterFall. Where the WaterFall line covers conventional chorus territory, the RetroVibe chases the Uni-Vibe-style pulse and pitch movement, with the mk.4's tap, ramp and expression features pushing it further4. For a broader look at the category, see Chorus Pedals and Vibrato Pedals.
Videos
JAM pedals
JAM pedals
Shawn Tubbs
Questions
Is the JAM RetroVibe mk.4 true bypass?
Yes. JAM Pedals lists the RetroVibe mk.4, including the Popped Art artwork edition, with true bypass switching, so your dry signal passes through untouched when the pedal is off.
Does the Popped Art RetroVibe sound different from the standard mk.4?
No. JAM Pedals states that its custom artwork versions, including Popped Art, Camper, Fishbone, Paths, Pink Eye and Skin, share the same sound and differ only in artwork. Each is a one-of-a-kind hand-painted piece, so the painting you receive will differ in detail from the photos.
Can you use tap tempo with the RetroVibe mk.4?
Yes. A separate TS input on the pedal accepts an external tap-tempo switch, and the onboard TAP/RAMP footswitch sets modulation speed when tapped. Hold the footswitch to ramp to a second speed, with the Speed knob setting the destination and Depth setting the travel time.
Is the RetroVibe mk.4 analog?
Yes. JAM Pedals describes the RetroVibe mk.4 as an all-analog Uni-Vibe-style modulation pedal, with an LFO range of 0.5 to 9.5 Hz.
What expression pedal works with the RetroVibe mk.4?
A TRS input on the pedal accepts a standard passive 10 kΩ expression pedal for continuous control of the Speed parameter. Any passive expression pedal with that 10 kΩ pot value and a TRS cable will work.
Sources (9)
- "Popped Art" RetroVibe mk.4, JAM Pedals (www.jampedals.com)
- Jam RetroVibe Mk4, Delicious Audio, 2026-02-11
- RetroVibe Mk.4 “My Mind’s Room” by Jam Pedals, RockBoard PedalPedia, 2026
- RetroVibe, JAM Pedals (jampedals.com)
- "Paths" RetroVibe mk.4, JAM Pedals (jampedals.com)
- "Pink Eye" RetroVibe mk.4, JAM Pedals (jampedals.com)
- "Fishbone" RetroVibe mk.4, JAM Pedals (jampedals.com)
- "Skin" RetroVibe mk.4, JAM Pedals (www.jampedals.com)
- New Pedals! Keeley Nocturne, Jam Retrovibe 4, Caroline Kilo 2K, DevTech Soft Drive, Hagerman EF86, That Pedal Show (YouTube), 2026-01-30
