A-111-2 Dynamic VCO
Vorankündigung / preliminary

A-111-2 Frontpanel
(prototype)

Latest news: The manual frequency control will be completed by a octave rotary switch (same as for A-110 and A-111) and the simple sine converter will we replaced by a better one (thanks to Tim Stinchcombe for his suggestion). Consequently the delivery date has to be postponed as both the electronics and the front panel layout have to be redesigned..

Additional sound examples of the prototype by Ingo Zobel: http://www.selfoscillate.de/modularexamples.htm


A-111-2 module scheme
(prototype)

Module A-111-2 is a very complex sound source. Though the front panel and scheme may look a bit complicated the design of the VCO is straight forward:

The main section of the module is a triangle VCO core (left bottom of the diagram). It has available the usual controls and inputs: manual frequency control (probably coarse and fine, and maybe an additional switch for VCO/LFO mode), CV1 with 1V/octave scale and CV2 for exponential FM. In addition a linear FM input with attenuator (probably with a switch for AC/DC coupling) and a hard sync input are available.

The second section of the module is the wave shaper (above the VCO core in the diagram). It derives the waveforms sawtooth, sine and two different rectangles with separate manual pulsewidth controls (manual PW1, PW2) and pulsewidth modulation inputs (CVPWM1, CVPWM2) with attenuators. We will see later why two different rectangles make sense. Separate outputs for triangle, sine and rectangle 2 are available. The waveforms sawtooth and rectangle 1 are internally processed. Details in the following paragraph.

Now we reach the two sections why the module is called a dynamic VCO: To begin with we have a voltage controlled waveform selector available. It is made of two switches that are controlled by a manual control (manual WF) and a control voltage input (CVWF) with attenuator. Four different states are possible: off, triangle, sawtooth or triangle+sawtooth. The signals are mixed together with rectangle 1 in a common adder. The output of this adder is marked composed waveform 1. The waveform selector is called "dynamic" as it is possible to switch within the waveform period. Any combination of triangle, sawtooth and rectangle 1 is possible. The pulsewidth control of rectangle 1 can be used to turn the rectangle off (fully CW or CCW).
Example: The rectangle 2 output is patched to CVWF input (probably the normalled patch in the module). This patch can be used to switch between sawtooth and triangle within one period. The pulsewidth of rectangle 2 defines the share of the sawtooth and the triangle signal (oscilloscope pictures and audio examples will follow).

The second dynamic section is the morphing or panning unit: Two opposite working VCAs are used to morph or pan between composed waveform 1 and an external input with attenuator called waveform 2. The external input will be probably normalled to the sine output. The panning unit has a manual control (manual Morph) and a control voltage input (CVMOR) with attenuator available. Even the morphing section is dynamic in that sense that it is possible to pan between waveform 1 and waveform 2 within one period. But of course the panning section can be controlled by slowly changing control voltages too (e.g. LFO or ADSR).
Example 1: The triangle output is patched to CVMOR input (probably the normalled patch in the module). This patch can be used to pan between waveform 1 and waveform 2 within one VCO period. Waveform 1 is the internally composed waveform (that may also be dynamically switched),  waveform 2 is any internal waveform (patched to waveform 2 socket) or any external signal (another VCO or noise or any more complex signal)
Example 2: The rectangle 2 output is patched to CVMOR input. Analog or digital noise is patched to the waveform 2 socket. This patch can be used to "insert" a short noise pulse into the waveform 1 (e.g. sawtooth). The duration of the "noise insertion" is controlled by the pulsewidth of rectangle 2.

Lean back, it's nearly done ...

The remaining sections of the module are standards for experienced A-100 users: a VCF (24dB lowpass filter with voltage controlled resonance) and a linear VCA. But there is one small special quality: the triangle output of the VCO section can be used to modulate the frequency of the filter in a linear (!) manner (in addition to the exponential control inputs CVF1 and CVF2). For this a manual control (manual modulation) and a control voltage input (CVMOD) with attenuator are available. One application is to run the VCF in self-oscillation without audio signal from the VCO and to modulate the filter frequency by the VCO with voltage controlled modulation depth.
The remaining VCF controls and inputs are standard: manual frequency control, exponential control voltage inputs CV1 with 1V/octave scale and CV2 with attenuator for exponential FM, manual resonance (emphasis) control, resonance control voltage input CVQ with attenuator for external resonance modulation.

The last section of the module is a linear VCA equipped with manual amplitude control and a control voltage input with attenuator (CVA). The VCA can be used for AM (amplitude modulation) applications - e.g. by patching the sine output of another VCO into the CVA input, but even for a normal loudness envelope by patching the output of an ADSR into the CVA socket.

Of course VCF and VCA can be used in the usual way to form a minimum synthesizer voice (VCO + VCF + VCA). Only the envelopes and LFOs are missing (e.g. A-143-2 and A-143-3 can be used to complete the synthesizer voice). But this was not the main idea behind the VCF and VCA in this module.

This is a preliminary information about the planned module. The features are still subject to change and all specifications are still preliminary without any obligation !


Breite/Width: ? TE / ? HP
Strombedarf/Current: ? mA 

Preis / Price: -
Liefertermin/date of delivery: The module will be probably not released
All features, specifications, prices, date of delivery are still without obligation
The price in US$ depends upon the exchange rate between Euro and US$ at the payment day. Free currency converter:

Sound Examples

These are the very first prototype examples. More samples and patch sketches will be added in the future.

The first example shows how the A-111-2 can sound like 3 rectangle VCOs: at the beginning only rectangle 1 without pulsewidth modulation (PWM) is heard. Then PWM1 is increased. In the end rectangle 2 with PWM is added. For this rectangle 2 is patched into the audio in 2 socket and the manual morph control is set to it's center position. The PWM1 and PWM2 control voltages are delivered by an A-143-3 (triangle outputs are used).


The second example is an AM application: The resonance of the filter is set to it's maximum for self oscillation and the filter is used as the main sound source. The triangle output of the VCO is patched into the CVA socket. Consequently the VCO modulates the sine coming from the filter. The output is processed by a VCA (A-131) that obtains it's envelope from an A-140. A MAQ16/3 is used as CV and gate source. CV is connected to CVF1 of the A-111-2, gate to the gate input of the A-140.


The third example shows dynamic waveform switching of the A-111-2: Again a MAQ16/3 is used as CV and gate source. CV2 and CV3 are patched to the CVWF and CVPW1 inputs of the A-111-2. Thus different waveforms and pulsewidth of the rectangle are possible for each step of the sequence. An envelope generator (A-140) is triggered by the gate output of the MAQ16/3. The envelope output is connected to the CVA and filter CVF inputs of the A-111-2. At the beginning no filter is used (manual filter control fully CW). Then the filter frequency is reduced manually and a little bit of the envelope is added to modulate the filter frequency. Only waveform 1 is used in this example (manual morph control fully CCW, no CVMOR), no filter FM, no filter resonance.


The next example is an AM application with an external VCO: The sine output of an A-110 is processed by a VCA (A-130) and fed into the CVA socket of the A-111-2. An LFO (A-143-3 subunit 1) is used to trigger an ADSR (A-140) that controls the A-130. The triangle output of this LFO controls PW1 of the A-111-2. Another LFO (A-143-3 subunit 2) is used to control PW2. Waveform 1 of the A-111-2 is sawtooth + rectangle 1, waveform 2 is rectangle 2 (patched into the the audio in 2 socket). The morph control is at it's center position. During the example the frequency of LFO1 and the time controls of the ADSR are changed.


The next patch uses some dynamic functions of the A-111-2 controlled by three CVs of an MAQ16/3: The gate ouput of the MAQ16/3 is used to trigger an ADSR (A-140). The envelope of the A-140 is patched to PW1 and CVA of the A-111-2 consequently controlling both the audio level and the pulsewidth of rectangle 1. CV1 of the MAQ goes to CVF1 of the A-111-2, CV2 to CVMOD. Consequently CV2 controls the linear filter modulation (different for each step of the sequence). CV3 is patched simultaneously into CVMOR and CVQ, and inverted (A-175) into CVF of the filter. The idea behind this patch is that for CV3 = 0V the filter is not used (frequency = maximum, Q = minimum) and the VCO signal of the A-111-2 is used. For CV3 = +5V the filter goes into self-oscillation and is used as sound source because Q is maximum and in the morph section the VCO is turned off not to "disturb" the filter. With values between 0 and +5V any combination of these extremes is possible.
At the beginning the modulations of CV2 (CVMOD) and CV3 (CVF, CVQ, CVMOR) are off. Then the modulation of CV2 is increased. In the end even the modulations of CV3 are added.


Next comes an example with both linear and exponential filter FM: At the beginning you hear the sequence without any filter FM. Then the manual control for linear FM in turned CW. After a while even the control for exponential filter FM (CVF1 of the filter) is increased, i.e. both FMs are now working. After a while the linear filter FM is removed and then even the exponential FM and you hear again the sound at the beginning. CVF1 of the filter is patched to a PLL (A-196) that is used to multiply together with an A-136 the frequency of the A-111-2.


The following patch is another example for complex dynamic functions of the A-111-2: The MAQ16/3 generates a sequence. CV1 goes to the CVF1 input of the A-111-2. Gate is used to trigger an A-140 envelope generator. The envelope of the A-140 is connected to CVF1 of the filter and to CVA. Three sub-units of an A-143-3 (triangle outputs) are used to control CVPW1 (slow LFO), CVPW2 (fast LFO) and CVMOR (slow LFO). The sine output is used as waveform 2. Rectangle 2 is patched to the CVWF input. Consequently one slow LFO controls the morphing between waveform 1 and waveform 2 (= sine). Waveform 1 is composed from a rectangle with a slow PWM and a dynamically switched sawtooth/triangle that is controlled by rectangle 2. The PW of rectangle 2 is modulated by a fast LFO. Linear filter FM is set to about 50%.


The next patch includes the sync function of the A-111-2: The MAQ16/3 generates a sequence. CV1 goes to the CV input of an A-110. The rectangle output of the A-110 is used to sync the A-111-2. The MAQ16/3 gate triggers an A-140 envelope generator. The envelope of the A-140 is connected to CVA. CV2 and CV3 of the MAQ16/3 are connected to CVMOR and CV2 of the VCF. The filter is used as sound source, i.e. Q is fully clockwise. At the beginning the connections of sync and CVMOR are not yet patched, i.e. only the sine of the VCF is heard with a loudness envelope generated by the A-140. Then the linear FM control is added, i.e. the VCF is modulated by the VCO signal - so far with a "clean" triangle. Then the sync connection is established. The triangle is reset at each positive edge of the A-110 rectangle. Consequently it is no longer a triangle and now the filter is modulated in a linear manner by the "synced triangle". After a while the CVMOR connection is patched also, i.e. at certain steps of the sequence the internal VCO signal "disturbs" the VCF sine as the VCO signal appears at certain steps at the filter's audio input. Then the modulations are removed again and the example ends as it began.


The last example shows the application of the A-111-2 within a normal sythesizer voice. CV and gate are generated by a MAQ16/3. Only an ADSR (A-140 triggered by the MAQ16/3) for CVF and VCA and two LFOs (two sub-units of an A-143-3) for PW2 and CVMOR are used. In addition CV2 and CV3 of the MAQ16/3 are used to control Q of the VCF and the linear filter FM CVMOD.


Waveform pictures (oscilloscope screen shots)
The upper section of all pictures shows the triangle waveform (VCO core) for reference. All pictures are made with a digital storage oscilloscope (DSO) with the A-111-2 prototype.
sine sawtooth sawtooth + triangle
sawtooth + rectangle 1 sawtooth + triangle + rectangle 1 triangle + rectangle 1
triangle + rectangle 1 (different PW) triangle + rectangle 1 (different PW) sawtooth + rectangle 1 (different PW)
dynamic switching between triangle+rectangle 1
and sawtooth (rectangle 2 is used as switch control)
dynamic switching between triangle+sawtooth
and rectangle 1 (rectangle 2 is used as switch control)
dynamic switching between triangle+sawtooth
and rectangle 1 (different PW)
dynamic switching between triangle and rectangle 1
(rectangle 2 is used as switch control)
inserting a noise share into the sawtooth wave by dynamic waveform switching
(rectangle 2 is used as switch control,
external noise is used as waveform 2/audio in 2)
dynamic switching and morphing between triangle+sawtooth and rectangle 1
(rectangle 2 is used as switch control,
triangle is used as morph control)
dynamic switching between triangle and rectangle 1
(rectangle 2 is used as switch control)
dynamic switching and morphing between triangle+sawtooth and rectangle 1
(rectangle 2 is used as switch control,
triangle is used as morph control)
dynamic switching and morphing between triangle+sawtooth and rectangle 1
(rectangle 2 is used as switch control,
triangle is used as morph control)
linear VCF modulation
(VCF in self resonance modulated by the triangle)
 
amplitude modulation (AM)
triangle is used to control the VCA
signal input of the VCA = self-oscillating VCF
amplitude modulation (AM)
triangle is used to control the VCA
signal input of the VCA = self-oscillating VCF