Birdkids The Bateleur MK 1 2022 - Black painted Aluminum

Lightly used, don’t want to sell it but I need the money.

Sounds super smooth and very fat.

Collin Benders go to Oscillator

The Birdkids The Bateleur VCO MK1 paired with its companion Filter/VCA Expander MK1 represents a high-end, premium-grade analog synthesizer voice architecture packaged across 30 HP. Designed in Austria, this duo combines a pristine, high-stability discrete oscillator with a rich, Roland-inspired 4-pole low-pass filter and full VCA articulation.

By joining these two modules via an internal ribbon cable, you eliminate the need for external patch utility overhead, turning a specialized performance oscillator into a powerful, self-contained synth voice.

Part 1: The Core — The Bateleur VCO MK1 (22 HP)

The foundation of the system is a massive, exceptionally stable discrete analog oscillator. While it provides gorgeous raw waveforms, its primary design focus is performance-oriented modulation and rich internal routing.

 Thru-Zero Frequency Modulation: Unlike standard oscillators that stall or exhibit unstable tracking when modulated heavily, the Bateleur features robust Thru-Zero FM. It allows the frequency to drop to zero and "flip" phase symmetrically, yielding incredibly musical, complex harmonic timbres, metallic textures, and deep bell-like FM tones without drifting out of tune.

 The Internal 24dB Filter: Built directly into the core VCO module is an onboard 4-pole low-pass filter. The Sine, Triangle, and Sawtooth waves can be individually routed or bypassed into this circuit using rugged toggle switches on the front panel.

 Performance Toggles: Designed for live manipulation, the module trades dense micro-controls for large, playable layout elements. Out of the box, parameters like resonance are binary (a toggle switch locks it immediately into pure, self-oscillating sine-wave generation), functioning as an instantaneous performance effect.

Part 2: The Unlock — The Filter/VCA Expander MK1 (8 HP)

While the main oscillator module houses the underlying filter and VCA core logic, its interface restricts granular access. The 8 HP Expander MK1 acts as a breakout board, translating internal parameters into fully attenuable manual knobs and independent CV patch points.

 Variable Resonance (Q) Control: The expander replaces the main module's binary resonance switch with a continuous manual potentiometer and a dedicated Resonance CV input (0–5V). This allows you to smoothly dial in everything from liquidy, subtle emphasis to screaming, overdriven squelch.

 Dedicated, Scalable VCA: The expander exposes the internal high-headroom VCA circuit to the front panel. It provides a manual VCA Initial Amplitude control (offset/drone bias), a VCA CV input with a dedicated attenuator (ideal for mapping an external envelope generator), an external audio input loop, and the master VCA Audio Output.

 Exponential FM Input: While the primary panel focuses on Linear FM, the expander introduces an attenuated Exponential FM input, perfect for classic sweeping pitch modulation, wide vibratos, and traditional cross-modulation behaviors.

 Secondary Cutoff Modulation: It adds an extra attenuated CV path straight to the filter cutoff, giving you the ability to modulate the filter with multiple distinct sources at once—such as tracking pitch from a sequencer while sweeping the filter with an LFO.