Concept
The goal was to keep the musical warmth and saturation of the original ladder filter design while making it fully compatible with Eurorack power, control voltage levels, and front panel ergonomics.
The YuSynth circuit served as the perfect starting point — a reliable, proven analog design known for its rich character and smooth resonance.
Design Approach
I started by analyzing the YuSynth ladder schematic, especially the transistor ladder core. Then I redesigned the PCB layout to:
- Fit a 10HP Eurorack panel width
- Use ±12V rails instead of ±15V
- Add standard Eurorack power header (10-pin IDC)
- Include input level control, CV attenuators, and resonance control
I kept the ladder section purely analog — no op-amp replacements, just discrete transistors to maintain that authentic analog tone and harmonic behavior.
PCB & Components
The board was built with matched NPN transistor pairs for the ladder to ensure stable cutoff response and low distortion.
I used high-quality film capacitors for the filter stages and metal film resistors throughout for precision and low noise.
The layout minimizes signal path length to reduce interference and retain analog purity.
Panel & Interface
The front panel follows a clean, symmetrical layout:
- Audio In / Out
- CV In 1 & CV In 2 (with attenuators)
- Cutoff and Resonance knobs
- Drive control for adding a touch of analog saturation
The faceplate was laser-engraved aluminum, matching the look of my previous Eurorack builds.
Sound & Performance
When tested, the filter delivered exactly what I hoped for:
A creamy, musical response with a deep resonance that can self-oscillate beautifully. The ladder topology gives that unmistakable Moog-style roundness, while the Eurorack voltage range makes it flexible for modern modular setups.
It handles both subtle tone-shaping and aggressive resonance sweeps with character and stability.
Closing Thoughts
This project bridges classic analog sound with modern modular format — a faithful YuSynth-inspired VCF Ladder Filter reimagined for Eurorack builders and performers.
