Doepfer A-111-3

Module A-111-3 is an extremely space-saving precision VCO/LFO with a 4HP panel only. Essentially it's the same basic circuit as the A-111-2 but with reduced features:

• triangle core
• fully analog design

min. 15 octaves pitch range in each mode (VCO/LFO):

• VCO mode: typ. 0.5 Hz - 20 kHz (with appropriate external CV)
• LFO mode: typ. 0.001 Hz - 40 Hz (with appropriate external CV)

• range switch so that the module can be used as VCO or LFO (in LFO mode all frequencies about 1/500 compared to VCO mode)
• about 24 octaves total in both modes (typ. 0.001 Hz - 20kHz)
• perfect 1V/octave tracking over min. 10 octaves (typ. 16Hz - 16kHz in VCO mode)

exponential frequency section:

Tune control

• selectable tune control range by means of an internal jumper: about 0.5 / 2 / 10 octaves
• manual VCO tune range (with jumper pos. 1, without external CV): about 16 Hz- 20kHz
• manual VCO tune range (with jumper pos. 2, without external CV): about 16 Hz- 70Hz
• manual VCO tune range (without jumper, without external CV): about 16 Hz- 22Hz
• if desired the min. frequency can be adjusted by the user (frequency offset trimming potentiometer, see note below)
• the corresponding frequencies in LFO mode are about 1/500 lower, the max. frequency in LFO mode is about 40Hz

• 1V/octave CV input "1V"
• exponential frequency modulation XM input with attenuator
• the XM input socket is normalled to a small positive voltage so that the XM control works as fine tune control when exponential FM is not in use. As a logarithmic potentiometer for finer resolution in the lower range is used, also the fine control is exponential (thank's to Václav of Bastl Instruments for this tip at Superbooth in Berlin)
• access to internal bus CV (via jumper, optional, please remove the bus jumper if this feature is not used to avoid unwanted frequency modulation as then the unused CV line of the bus works as a kind of antenna)

linear frequency section:

• linear frequency modulation input LM (without attenuator), DC coupled

Pulsewidth section for rectangle output:

• Manual pulsewidth control PW, adjusts pulsewidth from 0% (output = fixed at "low" state)
• up to 100% (output fixed at "high" state) Pulsewidth modulation input PM (without attenuator), about 5Vpp required for full PW range

Sync input SY (selectable hard or soft sync via internal jumper)

Waveform outputs:

• Sawtooth, rising edge, output level ~ 10Vpp (voltage range 0 ... +10V)
• Rectangle (controlled from pulsewidth section), output level ~ 10Vpp (voltage range 0 ... +10V)
• Triangle, output level ~ 10Vpp (voltage range -5V ... +5V, DC offset can be adjusted also also to 0 ... +10V)

• Nearly "perfect" waveforms (no glitches)
• LED (for display in LFO mode)
• only 4HP panel