The AJH Synths Matrix VCF & VCA is a 14HP Eurorack multimode voltage-controlled filter and amplifier module offering 16 distinct analogue filter types, 32 resonant filter variations via a switchable overdrive mode, and integrated CV-controllable VCA functionality, all inspired by and expanding upon the classic Oberheim Matrix 12 filter architecture. Versatile Filter Architecture The Matrix VCF delivers sixteen unique filter responses including low pass (1–4 poles), high pass (1–3 poles), band pass (2 and 4 poles), notch, all-pass, and complex hybrid modes. AJH Synth has expanded upon the original Matrix 12's fifteen filter types by adding a new four-pole all-pass filter (AP4), turning this into a fully featured phaser mode. Users can select filters manually via the Mode knob or with external CV input, which is attenuable via the front panel and visually confirmed by 16 dedicated LEDs, each corresponding to a filter type. P-Vox Mode – Distortion and Harmonic Complexity Engaging the P-Vox resonance mode radically transforms the behaviour and sonic character of the filter core. Borrowing inspiration from the Polivoks synthesiser, this analogue overdrive stage pushes all filter types into self-oscillation, regardless of whether they do so in standard mode. This mode introduces rich, harmonically saturated waveforms that can vary dramatically depending on the selected filter type, allowing the Matrix VCF to function as a tone-shaping oscillator. These oscillations are 1V/octave trackable over a usable 3–5 octave range. Integrated VCA for Compact Patching The module incorporates a built-in VCA directly after the filter output. When no CV is applied, the VCA remains fully open thanks to internal normalisation to +5V. Patching in external modulation sources such as envelopes or LFOs enables dynamic level control, with the Output Level knob serving as an attenuator. This integrated VCA reduces module count while still allowing flexible modulation and level control within compact systems. Comprehensive Control Inputs In addition to 1V/octave CV input for pitch tracking, the Matrix VCF includes two additional filter cutoff CV inputs that scale at 2/3 and 1/3 V/oct, offering nuanced modulation possibilities. Resonance CV input is also present, with the front-panel control serving as an attenuator. All CV inputs respond to voltages between 0 and +5V; negative voltages are ignored for stability and safety. User-Centred Interface Despite its vast feature set, the Matrix VCF prioritises usability with a logically arranged interface. A Mode knob and matching LED array simplify filter selection. Cutoff, resonance, input/output levels, and CV attenuation controls are all clearly labelled and ergonomically placed. The Peak LED alerts users when output levels exceed 10V p/p, aiding gain staging across the signal chain. High-Quality Construction and Power Efficiency AJH Synth maintains its reputation for rugged, reliable build quality. The module occupies 14HP of rack space and has a depth of 29mm including the power cable. Power draw is 56mA on the +12V rail and 36mA on the -12V rail, making it efficient enough for dense Eurorack systems. It is available in either Silver or Dark Edition panels to match system aesthetics.
