Electrosmith 3340 VCO

This is a straight analog oscillator built around a reissue of the Curtis CEM3340, the chip behind the SH-101, the Jupiter-6, the Prophet-5, the OB-8 and the Memorymoog. Electrosmith took the datasheet application circuit, folded in the tweaks the DIY community settled on over the years, and put the result on a submodule that drives this 6HP panel. If you have ever wanted that specific oscillator character in a rack without hunting down a vintage chip, this is the shortest route to it.

All four waveforms come out at once on their own jacks: sine, triangle, sawtooth and square. That matters more than it sounds, because you can take the sine to one destination and the saw to another without a multiple, or mix two of them for a shape the module does not offer on its own. Tracking is temperature-compensated and holds 1V/oct accurately over more than ten octaves, which is the part people actually notice - it stays in tune at the extremes where cheaper oscillators drift.

There are separate linear and exponential FM inputs, each with its own attenuverter, so you can dial modulation depth and polarity per input rather than fighting one shared amount control. The sync input is switchable between hard and soft: hard resets the waveform phase for the classic tearing sync lead, soft reverses it instead for something gentler and more hollow. Pulse width is adjustable for the square output, with an active clamp holding the duty cycle inside roughly 1 to 98 percent, so heavy PWM never drives the pulse into silence.

One thing to know before buying: this is a single voice, and a deliberately plain one. No wavefolder, no sub oscillator, no octave switch, no through-zero FM. It generates four waveforms very well and leaves the rest to the rest of your rack. It is also discontinued, so if you want a matched pair you would need to find a second one used.

This is the factory-assembled version, not the DIY kit. Electrosmith sold both, and the box label confirms which one this is - worth noting, because an assembled unit removes any question about build quality or soldering.

Condition: excellent. The grey panel is clean with no rack rash, the legending is crisp, all five controls turn smoothly, the sync toggle switches positively and the jacks are tight. The board is clean with the 3340 submodule seated as it left the factory, shown in the photos.

Included: the original Electrosmith box with its printed label, the original ribbon cable and two mounting screws.

Specs: 6HP wide, 37 mm deep. Current draw 38 mA on +12V and 27 mA on -12V, nothing on 5V. Simultaneous sine, triangle, saw and square outputs, V/Oct, linear FM and exponential FM inputs, switchable hard/soft sync, PWM. Eurorack format. Discontinued.

Shipping from the Netherlands, tracked. Offers welcome.