Doepfer A-111 High-end VCO 2 Video Tutorials by Raul Pena

For his next Doepfer tutorial video series, Raul Pena returns to the classics...

A-110 Standard VCO vs A-111 High-end VCO(2)

Module A-111-1 (VCO2) is a voltage controlled oscillator. 

The VCO has a range of about 12 octaves, and produces four waveforms simultaneously: pulse (rectangle), sawtooth, triangle and sine waves. 

The VCO's frequency is determined by the position of the range switch, tune and fine tune controls, and the voltage at the two pitch CV inputs, CV 1 and CV 2. Footage (the octave of the fundamental) is set by the Range control, which has seven octave steps. 

The Tune control is used for coarse tuning, and the Fine control for fine tuning of the VCO pitch. 

The A-111 can be modulated by both exponential and linear FM (frequency modulation). 

You can control the pulse width of the square wave either by hand, or by voltage control - Pulse Width Modulation, or PWM for short.
The A-111 also has inputs for Hard Sync and Soft Sync.

As the special circuit CEM3340 used in this module is no longer available the module has to be discontinued.

Doepfer A-111 VCO2 Tutorials (Playlist):

Check out Raul's latest survey at

http://www.surveymonkey.com/s/K3Z9PVF

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Oscillator Synchronizing

Interesting sound-effects can be obtained by the synchronising of (multiple) oscillators.
In a typical setup, one oscillator (master) restarts the cycle-period of the other one (slave) , what results in equal base frequencies on both oscillators. This is called Hard Sync.

The result is an irregular waveform with it's own harmonic spectrum, completely different from 'standard' waveforms

Soft Sync is a more general name for all kinds of oscillator synchronisation.
This form is very similar to Hard Sync, but here the slave oscillator is forced to reset to zero with every cycle of the master regardless of position or direction of the slave waveform, which often generates asymmetrical shapes.

In Soft Sync, rather than resetting to zero, the wave is inverted;  its direction is reversed.
Further variations to the sound can be made by comparing the sounds with different comparison tresholds. For more info see the Wikipedia page on Oscillator Synchronisation
Soft Sync sounds smoother  and distinctly different from hard-sync.
It is difficult to replicate this effect on digital synths, due to aliasing problems.

Soft Sync-like effects can also be created with other modules, for example a phaser or a Phase Locked Loop (PLL) Module.

Never Enough VCO's

The engines or hearts of all modular synthesizers are definetely the VCO's. As main sound source for your patches it seems you never have enough of them.

I own 5 VCO's at the moment, One A-111 High End VCO plus four A-110 Standard VCO's. Ideal for stacking layers of waveforms to make extra- fat sounds, and also very useable for multiple A-100 melodylines

The A-111 is the one i use most because of its extended possibilities. 

This VCO has an extended frequency range, improved waveforms, FM and Soft Sync inputs plus an extra fine-tune-controller. Ideal for controllerfreaks like me. 

It produces sine, triangle, pulse and sawtooth waveforms, which are all derived from the triangle oscillator, what does make it hard to produce perfect sine-waves ( but a little better as the A-110's sine wave )

One of the best things is that all 4 waveforms are all simultanously available at the outputs for your mixing pleasure.

The much cheaper A-110  has less controls and is based on a sawtooth oscillator. All outcoming waveforms of this module are derived from this sawtooth by internal waveform converters. This module also generates sinewaves that are not completely perfect, but to 'normal' ears this is hardly audible

I never noticed, and i guess most of us don't care and never noticed the imperfect-ness of the sinewaves of both modules.

Even on an oscilloscope it is hardly visible that the sinewaves are nothing more than rounded sawtooth-waves.

For a perfect sine wave Doepfer recommends the A-143-9 Quadrature LFO/VCO, another interesting module, that i will highlight in a future blogpost.

Note: As the special circuit CEM3340 used in the A-111 High End VCO module is no longer available the module has to be discontinued. Sales at Doepfer while stocks last !