CEM3340

The CEM3340 and CEM3345 are a self contained VCO, originally produced by Curtis Electromusic Specialties. With both exponential and linear control inputs and up to four output waveforms: triangle, sawtooth, square, and pulse with voltage controllable pulse width. It has full temperature compensation making it extremely stable. Also included is provision for hard and soft synchronization of the frequency, and an output for easy adjustment of high frequency tracking.

CEM3340/3345 differences

• The square wave output on the CEM3345 (pin 7) requires a pull down resistor to any negative supply greater than -4 volts.
• The frequency control is pin 15 on the CEM3340, pin 17 on the CEM3345.
• The precision multiplier output is pin 14 on the 3340, pin 16 on the 3345.
• The reference current input is pin 13 on the 3340, pin 15 on the 3345.
• The hi-frequency track is pin 7 on the 3340, pin 8 on the 3345.
• The threshold voltage pin is pin 9 on the 3340, pin 10 on the 3345.

Clones and equivalents

In 2016 after twenty or more years of diminishing availabilty, in response to Coolaudio's V3340 re-design of the part to the same specifications, OnChip Systems remanufactured the 3340.

Usage

To prevent the IC being put under too much stress if/when the outputs are shorted, all outputs should have a series 1K resistor. The triangle wave output is unbuffered and should never be used to drive an output directly, add a J201 FET follower to buffer it. A better sine output can be achieved by using instead the Thomas Henry VCO-1 waveshaper.

External links

• Tech note on improving PWM stability of the ALFA AS3340
• Precision Tuning of the AS3340 VCO by Rob Hordijk, September 2018
• The VCO-555 by Thomas Henry an approximation of the CEM3340
• CEM3340/3345 data sheet
• Picture of de-encapsulated defect CEM3340 at Stromeko Synth World
• Dual VCO (CEM3340-based, with thru-zero FM and various types of sync) by Juergen Haible
• Things to come: CEM3340 VCO, nonlinearcircuits, 17 August 2016
• CEM3340 VCO (Voltage Controlled Oscillator) designs by Tom Wiltshire, 27 August 2016
• ICs for Electro-Music (Part 1) by Charles Blakey
• A look at the VCO's of some famous analog synthesizers. by Chris Meyer, The Secret Life of Synthesizers, 25 Oct 2016
• Tuning the AS3340 by Rob Hordijk, 2018

Projects

• A really good AS3340 VCO design!! by Eddy Bergman
• Digisound 80-2 VCO, 1980
• Digisound 80-3 VCLFO, 1980
• VCO Deluxe by Thomas Henry, Polyphony, Nov/Dec 1981
• Low-Frequency VCO Gives Exponential Response by Thomas Henry, Electronics, January 13, 1983, pp. 168-169.
• Hyperflange + Chorus by Craig Anderton, Modern Recording & Music, Jul/Sep 1983
• Build a Precision Controller Clock by Thomas Henry, Electronotes, May/June 1984, Special Issue E, pp. 11-17.
• andrewF CEM3340 VCO, Mod Wiggler forum, Oct. 2016, for Eurorack
• TimoRozendal [pcb+panel] CEM3340 VCO for eurorack (8hp), Mod Wiggler forum, Oct. 2016
• Datasette OPECEM3340 – v3 (True Zero) on its way soon – Morph delayed, Mod Wiggler forum, Nov. 2016 and on Github, for Eurorack
• The VCO Maximus by Thomas Henry, 2017
• VCO CEM3340 PCB, Trilobite.audio
• Kassutronics VCO 3340 (eurorack)
• [ORDER] OCTOGINTA-II Digisound 80-2 eurorack version, Mod Wiggler forum, Feb 2018
• Digisound in eurorack and [ORDER] Digisound eurorack, Mod Wiggler forum, Mar 2018
• CEM3340 VCO Schematics and PCB!, Reddit/synthdiy, 28 Aug 2019
• Dusk work Self-Tuning VCO
• Electrosmith 3340 VCO submodule. SMT parts mounted on 0.1"/2.54 mm adapter PCB.