Behringer 921A Oscillator Driver Eurorack Module - Analog CV Control for 921B VCOs, 14HP

Drive up to 12 Behringer 921B oscillator modules with a single 921A Oscillator Driver, the analog heart of a massive modular synthesizer voice. This 14HP Eurorack module delivers precise frequency and pulse width control voltages with a pure analog signal path inspired by the legendary Moog System 55.

Overview

The Behringer 921A Oscillator Driver is a dedicated control hub for the 921B VCO modules. It provides all necessary CV outputs to manage frequency, pulse width, and synchronization across a bank of up to twelve oscillators. With a range switch spanning Lo, 16', 8', 4', and 2' settings, plus a fine frequency knob, you can dial in everything from deep sub-bass to soaring leads. A dedicated pulse width control and sync on/off switch give you complete timbral authority.

What stands out

• Pure analog design: Faithful reproduction of the classic Moog modular architecture for authentic vintage tone.
• Massive expandability: One driver can control up to 12 Behringer 921B oscillators, enabling huge stacked voices.
• Complete CV connectivity: Two frequency CV inputs, one pulse width CV input, and one sync input, plus three frequency CV outputs, three pulse width CV outputs, and one sync output.
• Flexible frequency control: Five-position range switch and dedicated frequency knob for coarse and fine tuning.
• Eurorack standard: Compact 14HP width and 45mm depth fits most Eurorack cases.

Technical details

• Module type: Analog oscillator driver
• Compatibility: Eurorack
• Inspired by: Moog System 55/35/15
• Module width: 14 HP
• Module depth: 45 mm
• Power consumption (+12V): 40 mA
• Power consumption (-12V): 20 mA
• Frequency CV inputs: 2
• Pulse width CV inputs: 1
• Sync inputs: 1
• Frequency CV outputs: 3
• Pulse width CV outputs: 3
• Sync outputs: 1
• Frequency control: Range switch (Lo, 16', 8', 4', 2'), frequency knob
• Pulse width control: Knob
• Sync control: Switch (on/off)
• Primary function: Drives up to 12 Behringer 921B oscillator modules
• Signal path: Pure analog

Our verdict

The Behringer 921A Oscillator Driver is an essential building block for anyone constructing a large-format analog modular synthesizer. Its ability to control up to twelve 921B VCOs from a single module makes it a powerful and cost-effective solution for creating massive, detuned oscillator stacks. The faithful reproduction of the Moog System 55 architecture ensures that the resulting sound is rich, warm, and authentically vintage. While it requires the companion 921B modules to function, the 921A is the central nervous system that brings them to life, offering precise control over pitch, timbre, and synchronization. For modular enthusiasts seeking to build a classic Moog-style voice, the 921A is an indispensable component.