*New in Box* Iconic MacBeth X-Series Backend Filter/Mixer/VCA/EG MK II Black - Fully Discrete Circuitry- Rare - Made in UK 🇬🇧

New-in-box iconic Macbeth Backend Filter X-Series. Mark II. Black. Rare.

On its way to becoming an elusive, sought-after vintage instrument.

Note: I’m also selling matching the X-Series Dual VCO MKII.

Summary:

The Macbeth X-Series Backend Filter MK2 is a high-end, discrete analog Eurorack module designed by Ken Macbeth. It functions as a complete "backend" for a synthesizer voice, combining a filter, VCAs, and envelope generators into a single unit. 

Key Features & Enhancements (MK2 vs. MK1) - The MK2 version introduces several technical upgrades and reliability improvements over the original: 

• Discrete Circuitry: Features a fully discrete transistor-based design using premium components, including selected bipolar transistors and audio-optimized capacitors for a "warm" vintage character.
• Feedback & Overdrive: Includes an external discrete amplifier normalized to the 2nd VCA. This allows users to feed the main output back into the filter’s input for saturated overload and harmonic distortion.
• Improved Build Quality: Upgraded from standard "box jacks" to higher-quality, more reliable jack sockets intended for a longer life cycle.
• Internal Routing: Now utilizes the Doepfer standard CV and Gate bus connectors on the back, which can be switched on or off discretely.
• Precision Components: Significant improvements in capacitor selection and precision-matched transistors for better consistency and sound quality. 

Technical Specifications

• Filter Type: 24dB/octave low-pass filter capable of self-oscillation.
• Outputs: Four distinct response outputs accessible pre-VCA for varied tonal shaping.
• VCAs: Two voltage-controlled amplifiers; the primary handles standard amplification (with analog overdrive potential), while the secondary is designed for dynamic control or velocity-like modulation.
• Envelopes: Two dedicated envelope generators for the VCF cutoff and primary VCA, including an inverted output for the VCF envelope.
• Power Consumption: Approximately 100mA (+12V) and 60mA (-12V). 

From Ken Macbeth:

The MACBETH X-SERIES MKII BACKEND FILTER is a dedication to quality and authenticity.

Discrete circuit design using premium components, including selected bipolar transistors and audio-optimized capacitors, ensures a purist approach to analog sound.

At the heart of the Backend Filter is a 24dB/octave low-pass filter, capable of self-oscillation and equipped with four distinct response outputs. These outputs are accessible pre-VCA, offering rich tonal shaping options for any patch. The filter tracks pitch via the TRACKING CV input, enabling seamless integration into melodic patches. A dedicated envelope generator drives filter modulation, with control over modulation intensity via the VCF EG/CV parameter.

The audio inputs on the Backend Filter are highly sensitive, contributing to its signature vintage character. These inputs can introduce subtle warmth or push signals into a pleasing saturation, perfect for adding depth to your sounds. Attenuators ensure precise control, allowing to maintain clean signals or explore driven, harmonic textures.

Complementing the filter are two voltage controlled amplifiers (VCAs), each with distinct roles.

The primary VCA delivers standard amplification with the potential for pleasant, analog overdrive when handling hot signals. The secondary VCA is ideally suited for velocity-like dynamic control or creative amplitude shaping.

The two envelope generators are dedicated to the VCF cutoff frequency and the primary VCA.

The envelopes generators also have output jacks for external patching. The VCF envelope features an additional inverted output.