The Sunnaudio Helion R2D3 is a preamp pedal with a built-in saturation circuit, made for both guitar and bass. Sunnaudio builds its units by hand in small batches1. Delicious Audio described the design, shown as a prototype at the NAMM 2023 show, as "a bass-oriented, high-end Swiss army device that works well also on guitar and any other instrument with a pickup"2.
The core of the pedal is a Drive circuit that Pedal of the Day describes as "articulate saturation that smoothly sweeps from 'clean' to 'saturation' to 'over-drive'"1. Around that sit a three-band parametric EQ, a Focus control for low-end recovery, and a Rabid control that pushes the drive toward fuzz. Bass Magazine's Jon D'Auria called it "the culmination of all of their previous preamps put into one package"3.
A preamp with saturation for guitar and bass
The Helion R2D3 is built as a multi-instrument preamp, with 5 Meg and 700K input impedance options to suit different pickups and instruments1. The EQ is a three-way parametric section with adjustable frequency for bass, mid and treble, which lets you target a specific problem or boost frequency rather than sweeping a broad fixed band1. There is also a selectable tuned EQ or shelving mode for speaker simulation, so the pedal can shape its output to behave like a speaker cabinet when going direct1.
The drive side is where the Helion R2D3 departs from a straight preamp/DI. The Drive knob "injects saturation when needed" and can be triggered by a second footswitch, so you can bring the drive in and out while the preamp and EQ stay active2. An internal diode dip switch selects between a low-gain setting, which works for bass and more subtle overdrive on both instruments, and a full overdrive setting for more distortion-like use1. A trim pot inside adjusts how much clean signal is blended into the Drive, with B for bass settings and G for guitar1.
For bass players, the pedal sits in a long line of Sunnaudio preamps, including the Rabbithead RH-1 and the Nucleus NU-1, and it carries their ideas forward into one box3.
The controls
| Control | What it does |
|---|---|
| Drive | Injects saturation when needed; can be triggered by the second footswitch2 |
| Tone | Shapes the color of the drive, placed after it in the circuit2; Pedal of the Day describes it as mid shaping for the Drive1 |
| Focus | Adjusts sub-harmonic frequencies to inject more low-end back into your signal1 |
| Rabid | Adds even more distortion and gain, bordering on fuzz tones at high settings1 |
| Parametric EQ | Adjustable frequency for bass, mid and treble1 |
| Footswitch 1 | Bypass or Mute mode1 |
| Footswitch 2 | Triggers the Drive2 |
Two internal adjustments shape the drive character before you ever touch a knob: the diode dip switch for low gain or full overdrive, and the clean/Drive trim pot with its B and G settings1.
What reviewers said
Bass Magazine's Jon D'Auria reviewed the pedal in March 2024 at a price of $475, and highlighted its compact size, noting it is less than half the size of most other preamp/DIs at 4.75 x 3.75 x 1.75 inches3. On the drive, he found that "even at this subtle setting, the clarity and articulation of the notes became crystal clear," and that pushing Rabid with Drive at about 4 o'clock gave the bass "a gritty-yet-clear tone"3.
Pedal of the Day, reviewing it in February 2025, pointed to its "transparently rich tonal qualities and subtle over-driven sounds"1.
"the R2D3 Helion is the culmination of all of their previous preamps put into one package"
Videos
Pedal of the Day
Delicious Audio
Questions
Does the Sunnaudio Helion R2D3 work for both guitar and bass?
Yes. It is described as a bass-oriented, high-end device that also works well on guitar and any other instrument with a pickup, and it offers 5 Meg and 700K input impedance for multi-instrument use. An internal trim pot lets you set how much clean signal stays in the Drive, with B for bass settings and G for guitar.
Can the Helion R2D3 run on a battery?
Yes. Alongside external 9 to 12V DC power and XLR phantom power, the Helion R2D3 supports battery power, so it can run without a power supply on a pedalboard or in a standalone gig rig.
Does the Helion R2D3 have an XLR output?
Yes. It has a 1/4 inch output and a balanced XLR output, and the XLR features an independent signal mode for console connection, which makes it usable as a direct box for recording or front-of-house.
What does the Rabid control do?
Rabid adds even more distortion and gain on top of the Drive circuit, and at high settings it takes the drive's distortion to the next level, bordering on fuzz tones. Bass Magazine's reviewer got a gritty-yet-clear tone with Rabid activated and Drive at about 4 o'clock.
Can the Helion R2D3 run on phantom power?
Yes. XLR phantom power is one of its three power options, alongside external 9 to 12V DC and battery power, so it can be powered directly from a mixing console over its XLR connection.
What does the Focus knob do on the Helion R2D3?
Focus adjusts sub-harmonic frequencies to inject more low-end back into your signal. For bass players in particular, it is a way to restore depth that drive and EQ shaping can take away.
Sources (3)
- Sunnaudio Helion R2D3 Guitar & Bass Preamp, Pedal of the Day, 2025-02-27
- New At NAMM 2023: Sunnaudio R2D3 Helion Preamp EQ, Delicious Audio, 2023-04-16
- Review: Sunnaudio R2D3 Helion Preamp, Bass Magazine, 2024-03-18
