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Modular Synthesizer VCO

Eurorack-format voltage-controlled oscillator with triangle core, waveshaper outputs (sine, saw, square, sub), hard/soft sync, and precision 1V/oct tracking using tempco resistors.

Project Duration 3 months
Status Completed
Year 2024
01

Bill of Materials

Component Part Number Quantity Notes
Op-Amp TL072 1 Precision integrator for triangle core
Matched Transistor Pair THAT340 1 Exponential converter
Tempco Resistor NTCLE203E3 1 3300 ppm/°C for V/oct compensation
Potentiometers Alps RK09 5 Frequency, PWM, etc.
Jacks Thonkiconn 6 3.5mm Eurorack jacks
Panel - 1 14HP aluminium, laser-etched
02

Tools Used

KiCad 7
PCB design with controlled impedance traces
Oscilloscope
Signal analysis and tracking verification
Soldering Station
Precision assembly of components
Frequency Counter
V/oct calibration and verification
03

Diagrams & Schematics

Core Schematic
Triangle core schematic with exponential converter
Waveshaper
Diode-ladder wavefolder for sine output
04

Assembly Process

1

PCB Fabrication

Designed PCB in KiCad 7 with controlled-impedance audio path and star-grounded audio/power domains.

2

Component Assembly

Soldered all components with attention to thermal management for the THAT340 matched pair.

3

Panel Installation

Installed 14HP aluminium panel with laser-etched labels and mounted potentiometers and jacks.

4

Calibration

Trimmed V/oct tracking to achieve ≥10 octaves within ±2 cents accuracy.

05

Oscilloscope Analysis

Triangle Core
Triangle Core Output
Clean triangle wave from precision integrator core.
V/oct Tracking
V/oct Tracking Test
Demonstrating ±2 cents accuracy over 10 octaves.
06

Resources & References

Yusynth VCO Design

Classic triangle core VCO design reference.

Eurorack Power Standards

Official Eurorack power supply specifications.