• Clone of the Sequential Circuits Pro-One (1981-1984)
  
• Desktop Synthesizer
• Analog
• Two oscillators with CEM3340 ICs
• Noise generator
• Mixer
• 24dB Curtis filter (lowpass)
• Two ADSR envelopes
• LFO with three waveforms
  
• Modulation bus
• Audio input
• Arpeggiator
• Sequencer
• CV/Gate inputs/outputs
• USB & MIDI
  

Connectors (for modular use)

Inputs

• Mod MW CV (replaces the modulation wheel in the modulation bus)
  
• OSC CV (CV input pitch control)
• Gate/CLK (clock input for sequencer & arpeggiator)
• LFO CV (CV input for LFO speed)
• EXT (audio input)
• Cutoff CV (CV input for cutoff)
  
• Resonance CV (CV input for resonance)
  

Outputs

• LFO Shape (CV output of the LFO)
  
• KB CV (CV output pitch)
• Gate (Gate output)
• Mixer (audio output of the mixer)
• Filter Env (CV output filter envelope)
  
• Amp Env (CV output VCA envelope)
• Phones (headphones output)
• Audio Out (instrument output)
• MIDI, USB and Main Out 6.3 mm jack on the rear panel
  

The Synthesizer

The two assertive oscillators, each based on a CEM3340 chip, each have sawtooth and square waveforms, an octave switch, fine tuning and pulse width controls. Oscillator A can be synchronized to oscillator B, the second tone generator is additionally equipped with the triangle waveform and can be switched to low mode as well as disconnected from the pitch control. Both VCOs are combined in the mixer, here you also find the noise generator, which can be replaced by an external signal. The nice basic sound is processed with a characterful 24dB lowpass filter, which is also known as Curtis VCF. It behaves similar to a Moog filter, but sounds different from the transistor cascade due to the IC CEM3320 used. The two crunchy ADSR envelopes are permanently assigned to filter and VCA. An LFO with three waveforms is connected to the destinations via the modulation bus. Among the special features of this instrument are the waveforms that can be activated simultaneously in both oscillators and the LFO.

Modulations Bus

The modulations are assigned on the left of the control panel. The filter envelope, oscillator B and the LFO are available as parallel sources, each with its own attenuator. Via switches these are assigned to the destinations frequency oscillator A+B, pulse width oscillator A+B as well as cutoff directly or via the modulation wheel (or midi controller). Used carefully, wild oscillator drifts, sync sounds, sirens, FM for filter and/or oscillator A as well as pulse width modulation are possible. Turn it all up at once and it gets really wild! The modulation bus is the hottest feature besides the sound of the Pro-1.

Sequencer & Arpeggiator

The ingeniously simple sequencer grants access to two patterns, each of which can be up to 40 steps long; pauses can also be programmed. The notes for this are played in via a connected MIDI keyboard. After input, the patterns can be transposed with the keyboard. The arpeggiator primarily offers the playback modes Up and Up&Down, but can also be integrated into the pattern. The synchronization to other equipment is done via the analog clock input or MIDI/USB.