Eric Archer's Rare Waves has built a reputation for thoughtful analog designs, and the Hydronium proves that you don't need to clone the TB-303 to capture its spirit. This is an all-new circuit that reimagines acid synthesis for modern producers, available in both desktop and Eurorack formats.
The heart of the Hydronium is elegantly simple: a single voltage-controlled oscillator with sawtooth, square, and pulse-width modulation waveforms feeding into a resonant 12dB low-pass filter paired with a decay envelope. You get the essentials that made acid basslines legendary—programmable glide for those signature pitch slides and dynamic accents to punch individual notes—but the design extends beyond pure homage. The envelope switches between trigger and gate modes, letting you shift from sequenced acid patterns to bright, articulate lead sounds. Control comes via MIDI with a proper 5-pin DIN socket or CV-Gate, and there's a built-in MIDI-to-CV converter with post-glide v/oct outputs that lets you use it as a bridge to other analog gear.
One of the Hydronium's smartest features is the audio effects loop positioned between the filter and VCA. This placement means you can run distortion, phaser, or other high-gain effects without the self-noise that typically comes from patching effects at line level. The pre-VCA effect return keeps your dynamic range intact even when you're pushing things hard. The Eurorack version spans 28 HP with patch points organized along the left side, while the desktop edition comes in your choice of yellow, blue, or black. Both formats are available pre-assembled or as kits with over 200 components, making it accessible whether you want it ready to go or prefer building it yourself.
Since its release, the Hydronium has earned respect in the acid and techno community for its genuine analog character and surprisingly deep sound design for such a focused instrument. It's become a favorite for producers who want authentic acid without the vintage price tag or the limitations of a strict clone.
