North Coast’s complex VCO is comfortable on a journey to the East or West Coast, while providing a stable foundation at home in any Eurorack. The module contains two triangle-core VCOs, each with four waveforms and standard V/octave control. As basic VCOs running independently these can be the heart of a traditional subtractive East Coast synthesizer. But the Middle Path’s oscillators can also be used together, with or without sync, to drive its unique multi-output Gilbert-style sine shaper. The shaper, which can also take external input, offers wave shaping, distortion, folding, phase modulation (including through-zero), and imitation stereo. These effects take the sound into West Coast territory.
The design emphasis is on harmonious combination of simple principles. The exponential converter uses premium analog multipliers and a transistor array to ensure temperature stability without fiddly adjustments or hard-to-control “tempco” resistors; it should provide consistent tracking, and especially between the two oscillators, without needing to warm up. The triangle cores are intrinsically frequency-accurate without needing extra circuitry to compensate for reset time. The sine shaper includes our own novel quadrature modification which can be used to generate a stereo signal or in combination with other modules to create frequency shift effects. The sync circuit joins the oscillator cores in another way with a selection of soft and firm modes.
Middle Path VCO – Build Document
- All-new design, not a clone or imitation of anything else. Innovative quadrature sine shaper offering through-zero phase modulation with a range of up to 1080°
- Genuine AD633 and THAT320 chips in the exponential converter; sockets on all DIP ICs
- Normalization to the Eurorack bus allowing it to receive pitch control without needing an input patch
- High-quality potentiometers with bushings fastened to the panel for wobble-free operation; conductive plastic for smooth feel
- Through-hole for easy hand construction and maintenance
- Connectors between boards, and panel controls mounted on a board – no flying wires
- No compromises on build quality: real aluminum panel with colour printing; panel screwed solidly to both the PCBs and the pots and jacks, for maximum ruggedness; nickel and gold plating on the circuit boards; close-tolerance metal film fixed resistors.
- Fully open design – no lock-in
- 24HP Eurorack synthesizer module, 36mm deep including space for the power cable.
- Maximum current requirements in normal use: 75mA +12V, 105mA -12V. 16-pin power cable with polarized connectors, and protective diodes on the ±12V rails.
- Build difficulty: intermediate. All through-hole. Multimeter and oscilloscope are recommended for adjustment.