Molten Music Technology Burns Through the AJH Gemini 2412: Dual SEM Filter Mayhem

Here’s where things get bonkers: the Gemini’s feedback circuit. Unlike classic SEMs, this one lets you dial resonance so far it’ll start self-oscillating like it’s trying out for a sine wave Olympics. Robin’s first encounter with the module left him scratching his head—he wanted silky resonance, not a screaming oscillator. Surprise! The feedback mod comes pre-installed (via back-panel jumpers), and it’s utterly wild when engaged.

Disabling the feedback circuit brings back the classic, smooth SEM behaviour, but if you’re craving madness, leave it on and hang on to your knobs. The only catch? You have to yank the module out of your rack to flip those jumpers—no front-panel switch, which is a proper faff. Still, for those who love to live dangerously, the Gemini can go from polite filter to feral noise-beast with just a little fiddling (and a screwdriver).

This filter isn’t just about raw power—it’s got style. Robin demonstrates how the Gemini’s sound is all about that Oberheim smoothness, with a silkiness and restraint that’s hard to fake. Even with all the modulation options—envelope, LFO, sequencer CVs—the core sound stays sweet. You get low pass, band pass, high pass, and even a variable mode that sweeps between them, letting you sculpt tones from vintage warmth to shimmering modern textures.

The filter’s controls have proper bite. Push the input past 8, and things start to overdrive—perfect for those who like their analog dirty, not dainty. Modulation is flexible but not overwhelming, so you can get weird without getting lost. Whether you’re after classic sweeps or more experimental fare, the Gemini’s character never turns to plastic. It’s a filter with taste—and just enough attitude.

Robin doesn’t just talk theory—he gets gritty with patch cables and shows what the Gemini can really do. From running two oscillators through each filter side to blending waveforms with CV, the module’s architecture unlocks all sorts of stereo and serial filtering games. Mixing, modulating, and inverting between channels—this is where modular gets fun and a bit chaotic.

But don’t expect a plug-and-play experience. Understanding how the dual filters interact, especially in cascade mode, is key. Robin finds the sweet spot for stereo width, formant filtering, and creative signal mangling, but he’s honest about the learning curve. If you want to see the full madness—and hear those wild resonance shrieks—you’ll have to watch the video. Words don’t do justice to a full-on Gemini jam session.

So, where does the Gemini 2412 land in the world of modular mayhem? Robin’s not shy about the trade-offs: it’s a big module, and the dual-filter setup can be overkill for the minimalist. But if you’ve got the rack space and a hunger for Oberheim tones with a modern twist, it’s a serious street weapon. The feedback circuit is both blessing and curse—brilliant for experimentalists, annoying for those who just want instant creamy sweeps.

Robin’s verdict? The Gemini 2412 is a luxury filter for those who know what they want and aren’t scared of a little chaos. It may not be for everyone, and a front-panel feedback switch would’ve been nice, but the sound and flexibility are undeniable. If you want silky resonance, stereo tricks, and the option to go full toaster-fight, this filter delivers. Just be sure your rack—and your ears—are ready.