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Synthesizer Printed Circuit Boards

TH-102 “El Cerrito” 2206-based Voltage-Controlled Oscillator

Another project from Thomas Henry?s circuit-packed book, An Analog Synthesizer for the 21st Century, the TH-102 is a very versatile VCO based on the Exar XR2206 VCO chip. One unusual feature is the ?Skew? waveform modulation that allows you to morph the triangle wave to a +1 octave ramp wave under voltage control. If the Sine wave output is selected, the Skew feature will morph the waveform from a Sine to a +1 octave Ramp-like wave (with s-shaped segments). Check out the graphic below for a better idea of the unusual waveforms available from the El Cerrito.

  • Tri to Ramp or Sine to Ramp Out (switch selectable)
  • Pulse Out (derived from Tri / Sine)
  • Suboctave (derived from Pulse)
  • Square Out
  • Suboctave (derived from Square)
  • Rampoid Out

  • Two Expo FM Inputs with attenuators
  • Linear CV Input with attenuator
  • 1V/Octave CV Input
  • High / Low range switch.

  • Tri - Ramp Skew CV Input with attenuator
  • PWM Input with attenuator

  • Sync Input

The LFO range goes from 0.05Hz (20 sec/cycle) to 1.63KHz, and the audio range goes from 0.5Hz (2 sec) to 16.2KHz. Great range and a buncha waveforms.

While working with our prototypes, we've figured that it is possible to get three octaves of tones from the TH-102 — simultaneously! If you turn the Skew control all the way up, the Tri/Sine output will sound one octave up from the “fundamental” note. Since the Pulse wave is derived from the Tri/Sine, it will also be one octave up. The Rampoid and Square waves will be at the “fundamental” tone, and so will the Pulse suboctave. And finally, the Square suboctave will be one octave below the “fundamental” tone. The Tri/Sine and the Pulse will change octaves depending on the setting of the Skew control, as will the Pulse suboctave. All sorts of fun!

The PCB is available for do-it-yourselfers. It is not difficult to build compared to other synthesizer modules, but Magic Smoke does not recommend this for your “first bulid”.



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TH-102 PCB (printed circuit board). 4" x 5" (102mm x 127mm), double-sided, with blue solder mask. Meets RoHS standards.

TH-102 Revision 2 boards are in-stock and shipping.

Boards are US$20 each. Shipping and handling charges are shown, below.

Quantity of PCBs
Destination 1 or 2 3 or 4 6 to 8
US / Canada $3.50 $5.50 $7.50
EU / UK / Aus $6.50 $8.50 $10.50
Other Please inquire.
Shipping and handling charges apply to the
total quantity of PC boards in the shipment.

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Specifications and prices are subject to change.

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