Gear Hunter

MINIATURE SYNTHESIZER VOICE

Description

The A-111-6 Miniature Synthesizer Voice from Doepfer is a compact and fully-fledged synthesizer voice. The foundation of the A-111-6 is a triangle core VCO that features pitch control and an octave switch to select up or down one octave. A mod CV input features an attenuator and destination switch that chooses between pulse-width modulation, frequency modulation, or in the middle position to turn the modulation off. The pulse width can also be set manually. The waveform switch selects between sawtooth, triangle, and off.

The selected waveform is summed with a pulse wave and then both are fed into the VCF. The VCF is a 24dB lowpass filter with frequency and resonance control. At high resonance settings, the filter begins to self oscillate. Two FM inputs are present: FM 1 features an attenuator to control modulation depth and FM 2 approximately tracks 1 v/oct. This is particularly useful with the filter self-oscillating. With nothing patched into FM 1 the envelope’s output is normalized to it and is attenuated by the FM 1 control.

The envelope features a switch that selects between A/D, ADSR, and A/R. There are controls for attack and decay/release time and a CV input labeled CVT. A jumper on the back of the module selects whether the CV affects the attack time only, the decay/release time only, or affects all settings at the same time. Another internal jumper sets whether positive CV lengthens or shortens the envelope time. The sustain level is set at a constant 50% in ADSR mode.

The balance section is comprised of two VCAs, a balance control, and a balance CV input. The VCO’s output is hardwired into VCA1 and the external input is connected to VCA2. With nothing patched into the external input, a sub-octave pulse wave derived from the VCO’s pitch feeds VCA2. The balance knob and CV input control which VCA signal is present at the output of the balance section. In the middle the two signals are of equal amplitude. Counterclockwise from the middle VCA1 is emphasized and clockwise VCA2 is emphasized. The output of the balance is hardwired to the VCF input.

The final output VCA has a gain control that sets the initial gain level. A switch controls whether the VCA is controlled by the internal envelope, gate signal that bypasses the envelope, or by manual gain control only for droning the module. In the external gate mode, some potentially unwanted clicking may occur. In order to minimize this, a jumper on the back of the module can be set to add some slew limiting to the gate input. The VCA has some non-traditional response characteristics, between -90dB and -20dB the response is exponential and from -20dB to 0db the response is linear.

Complete synthesizer voice
Triangle core VCO
AD, AR, or ADSR envelope with CV control
Balance control blends between internal VCO and external input or sub-oscillator
VCA with unique response curve
24dB lowpass filter
Filter resonance goes into self-oscillation at high settings