A-135-2 Quad Voltage Controller Filter/Mixer/Panner
Vorankündigung / preliminary

A-135-2 Front Panel version 1

This is the first draft of a new module that can be used for versatile filtering, mixing and panning functions. Each of the four channels has these sub-units available:

• 24dB lowpass with adjustable resonance
• main VCA (loudness VCA)
• two opposite working panning VCAs

The sub-units (VCF/ main VCA / panning VCAs) are daisy-chained and the outputs of the panning units are mixed together to obtain a common left and right audio output.
Each parameter (frequency, resonance, amplitude, panning) has available a manual control but can be controlled also by an external voltage. For this sub-unit board is equipped with a pin header that can be connected to an external CV In option. Two different versions of CV In options are planned:

• a simple version without attenuators, i.e. nothing but a jack socket for each parameter (see bottom left picture, this module is required only once as all 16 CV inputs are available) 
• another version that contains 4 CV inputs with attenuators (see bottom right picture, this expansion module is required for each sub-unit of the main module)

Both CV expansion modules can be combined (i.e. it is possible to add CV inputs with and/or without attenuators).

That way the module can be used only for manual control only or for manual and CV control with or without CV attenuators. It's also possible to add the CV In option with attenuators only for one or a few of the channels. No soldering is required to add the CV In option(s) to the main module. The desired CV In option(s) are simply connected to the main module with ribbon cables.

Even several A-135-2 can be combined to obtain a system with e.g. 8, 12 or 16 inputs with common left/right outputs.

If the filter cutoff control is fully cw and the filter resonance control fully ccw the module is working as a mixer/panner without filter.

The module can be used also for polyphonic patches as a fourfold final VCF/VCA unit.

The quad modulation sources A-143-1 Quad AD, A-143-2 Quad ADSR and A-143-3 Quad LFO  are suitable modules to generate control voltages for the the A-135-2. But even other CV sources can be used, e.g. sequencer A-155, joy-stick A-174, midi-to-CV, random voltages A-118 or A-149-1, Theremin A-178, ribbon-controller A-198, morphing controller A-144, S&H A-148, envelope follower A-119 and envelope generators A-140, A-141, A-142 and other CV/modulation sources.

Modifications version 2 vs. version 1:

• Audio input level control (only a plastic shaft without knob to save space)
• Mute switch (sets VCA amplification to zero)
• control voltage inputs for frequency, level (VCA) and panning at the bottom of the front panel

Because of these additions the front panel will become wider. We payed attention that all cable connections are at the bottom to have free access to the manual controls as the module is planned in the first place as an output mixer. The fourth CV input for resonance had been omitted to keep the panel width as small as possible.

Modifications of version 3 vs. version 1/2:

• modular version of the filter/mixer/panner
• separate sub-modules for main, filter converter and audio output modules
• main module: contains VCF (low pass), VCA, VC panning unit, audio input with level control (only a plastic shaft without knob to save space), mute switch (sets VCA amplification to zero) and control voltage inputs for frequency, level (VCA) and panning at the bottom of the front panel
• filter converter module: this module can be added to the main module and makes available 16 different filter types (sub-set of the A-107 filters), the filter type is chosen by a 16-position rotary switch, in addition a bypass switch (bypasses the VCF) and a separate VCF output (pre VCA/Pan) are available, the module is connected internally via a ribbon cable to the A-135-2a (no soldering required)
• audio ouput module: this module is used to add up the left and right signals of all modules

Advantage of this modular approach:

• any number of main modules can be combined (not fixed/limited to four)
• a filter converter module can be attached to each main module to obtain more filter types for this main module
• more flexibility as the system can be adjusted to the user's conception

Disadvantage of this modular approach:

• more expensive because of the many front panels

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 !

A-135-2 Front Panel version 2

A-135-2 Front Panel
(CV expansion module without attenuators)

A-135-2 Front Panel
(CV expansion modulewith attenuators)

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