AJH Synth Official’s MATRIX VCF & VCA: Vintage Filter Versatility for the Modern Eurorack

AJH Synth’s MATRIX VCF & VCA lands in the Eurorack world as a 14hp module, available in both black and aluminium finishes. It’s a faithful analog reimagining of the iconic filters found in the Oberheim Matrix 12 and Xpander synths of the 1980s—machines revered for their power and flexibility in both pop and film music circles. The video opens by situating the module firmly in this vintage lineage, while making clear that the design is entirely analog, despite the digital control heritage of its inspiration.

The presentation highlights how the AJH module brings all the complexity of the original filter modes into the modular domain, but with hands-on immediacy. The inclusion of a Polivoks-inspired resonance and distortion circuit is a notable twist, offering a dramatic shift in character at the flick of a switch. This addition pushes the module from smooth and classic into aggressive, self-oscillating territory, giving it a true Jekyll and Hyde personality within a single panel.

The MATRIX VCF & VCA houses all 15 filter types from the original Oberheim design, and then goes one better with a 4-pole all-pass mode. This broadens the sonic palette, making it a playground for anyone who likes to sculpt and mangle audio in creative ways. Each mode is selectable via a front-panel pot or by external CV, with a ring of 16 LEDs providing instant visual feedback on the currently active type.

AJH Synth’s approach means that filter mode selection isn’t just a static choice—it’s a modulation destination in its own right. The video demonstrates how switching between modes can introduce clicks due to phase differences, a side effect of the analog architecture that seasoned patchers will recognise. The ability to automate mode changes via CV opens up evolving textures and rhythmic filter sequences that go far beyond the classic static low-pass sweep.

Control is king here, with four separate CV inputs for frequency, including the classic 1V/octave, plus dedicated inputs for resonance and filter mode. The video shows how these can be patched for everything from subtle movement to wild, automated shifts. Frequency can be modulated by envelopes, sequencers, or random sources, while resonance can be CV’d for dynamic emphasis or even pushed into self-oscillation for melodic duties.

The filter’s behaviour under modulation is explored in detail, with examples of using sequencers to select filter modes per step, or envelopes to shape both the filter cutoff and the VCA. The inclusion of attenuators for each CV input ensures fine control, allowing for nuanced patching. The result is a module that invites experimentation, whether you’re after evolving pads, percussive blips, or screaming leads.