258D Dual Oscillator PCB
The 258D Dual Oscillator PCB is a two layer, ENIG plated board designed to replicate the functionality of the Buchla 258C module using modern construction techniques and readily available parts. It can be used with any 258 panel, but we recommend the panels available here which have the correct cut out for the calibrated V/O inputs – third party panels will need this hole drilling out by the builder.
Like Mark Verbos’ 258V and Dustin Stroh’s 258J, the 258D uses the exponential converter and triangle core from the Electronotes VCO option 3, designed by Bernie Hutchins, with output waveshaping derived from Don Buchla’s original 258 Design.
Additionally, the 258D includes:
• A stable voltage reference to isolate the frequency controls from fluctuations and noise on the power supply rails
• High frequency compensation for improved tracking
• A scaled V/O CV input in place of the original scaling potentiometer
• The option to select either saw or square waveshapes for each oscillator by setting a jumper on the rear of the module
• A buffered copy of the triangle core replacing the rightmost output of each oscillator
The 258D is designed to be suitable for hand assembly, but it is not recommended as a “learn surface mount” starting point. You should at a minimum have a temperature controlled soldering iron with a reasonably fine point and good quality solder 0.5mm diameter or finer. Some form of magnification may be beneficial for placing and inspecting the SOT-363 packages.
Full documentation is available from https://www.github.com/DunningtonAudio/258D