Model 1011 Discrete Oscillator

The Slightly Nasty Model 1011 is a voltage controlled oscillator that’s a little bit different. Despite featuring a host of functionality including four mixable waveshapes, suboctave, linear and logarithmic FM, pulse width modulation, and oscillator sync, inside it you won’t find a single IC opamp or OTA. What you will find is no less than 41 discrete transistors flying in close formation, doing their best to output useable musical tones.

The Model 1011 has been designed from the ground up to use modern “jellybean” components that can be cheaply and easily obtained from most electronics suppliers. Despite the unusual implementation, the architecture is actually a very traditional sawtooth-core design that will be familiar to most people who have worked on VCOs before.

Three outputs provide mixable sine-triangle, saw-pulse-suboctave, and suboctave square respectively, the pulse wave also featuring both manual and CV-controlled symmetry (pulse width). Aside from the usual 1V/Octave input, there are also separate inputs for both linear and logarithmic FM, each with input attenuators, as well as a hard sync input. The exponential converter is temperature compensated for better thermal stability and the sawtooth core features high-frequency compensation for better pitch tracking.

The Model 1011 uses the Loudest Warning 4U format for the front panel, and follows Eurorack electrical and power standards. All front panel components are PCB mounted for easy wiring-free construction. The front panel is available in two finishes – satin anodised and gloss white powdercoat.

Updates: v1.1 PCB removes bodge resistor and features modified output stages. The v1.1 documentation has new values for R313, R316, and RV202 that can also be applied to v1.0 PCBs to provide better sine shaping and high-frequency compensation.

Current Documentation (Rev A for PCB v1.1):

> Manual and BOM updated 30th July 2021 to note that BC550C and BC560C transistors (now discontinued) can be replaced with BC547C and BC557C respectively.

Model 1011 Construction Manual

Model 1011 Schematics

Model 1011 BOM

Older Documentation (Rev B for PCB v1.0):

Model 1011 Construction Manual (Legacy)

Model 1011 Schematics (Legacy)

Model 1011 BOM (Legacy)