SequentialOB-6 Polyphonic Analog Synthesizer Desktop Module

Sequential OB-6 Desktop

The OB-6 Desktop Module is a lighter version of Dave Smith and Tom Oberheim’s popular OB-6 keyboard. The desktop version features 6 voices, each with 2 VCOs that are modeled after those on the original SEM. Each VCO features multiple, continuously-variable waveforms; VCO 1 contains a sawtooth and pulsewidth wave (complete with PWM), while VCO 2 features all of those as well as a triangle wave. Additionally, VCO 2 doubles as a master LFO that can be used to modulate various parameters.

The unit boasts DSI’s unique SEM multimode filter, which is continuously variable from notch to lowpass to highpass with switchable bandpass functionality. The OB-6 also has VCA and filter envelope sections with velocity sensitivity and various modulation options, a noise generator circuit, and onboard mixer section with a sub-oscillator routed to VCO 1. There is the X-Mod section (capable of audio-rate modulation), and a digital effects section (reverbs, delays, ring modulator, flanger, and phase shifter) sourced from the Prophet 6.  All that combined with the internal arpeggiator and polyphonic step sequencer gives the OB-6 a lot of punch in a small package

OB-6 Desktop Features

OSCILLATORS

• Two discrete VCOs per voice
• Continuously variable wave shape (sawtooth and variable-width pulse, plus triangle on oscillator 2) per oscillator
• Pulse width per oscillator
• Hard sync: oscillator 1 syncs to oscillator 2
• Square wave sub-octave generator (oscillator 1) per voice
• Low frequency mode (oscillator 2)
• Keyboard tracking on/off (oscillator 2)
• Oscillator detune amount for increased tuning instability, from subtle to extreme

MIXER

• Oscillator 1 amount
• Oscillator 1 sub-octave amount
• Oscillator 2 amount
• White noise amount

STATE-VARIABLE FILTER

• Two-pole, resonant, filter per voice with low-pass, high-pass, band-pass, and notch functionality inspired by the original Oberheim SEM filter
• Bi-polar filter envelope amount
• Velocity modulation of envelope amount
• Keyboard tracking: off, half, full

FILTER ENVELOPE

• Four-stage (ADSR) envelope generator
• Velocity modulation of envelope amount

AMPLIFIER ENVELOPE

• Four-stage (ADSR) envelope generator
• Velocity modulation of envelope amount

LOW FREQUENCY OSCILLATOR

• Five wave shapes: triangle, sawtooth, reverse sawtooth, square, and random (sample and hold)
• Clock sync (internal or external MIDI clock)
• Initial amount
• Mod destinations: oscillator 1 frequency, oscillator 2 frequency, oscillator 1 and 2 pulse width, filter cutoff, filter mode

X-MOD

• Sources: filter envelope (bi-polar) and oscillator 2 (bi-polar)
• Destinations: oscillator 1 frequency, oscillator 1 shape, oscillator 1 pulse width, filter cutoff, filter mode

AFTERTOUCH

• Source: channel (mono) aftertouch with bi-polar amount
• Destinations: oscillator 1 frequency, oscillator 2 frequency, LFO amount, amplifier envelope amount, filter envelope amount

CLOCK

• Master clock with tap tempo
• BPM control and display
• MIDI clock sync

ARPEGGIATOR

• Selectable note value: 16th note, 8th note triplet, 8th note, dotted 8th note, quarter note
• One, two, or three octave range
• Up, down, up/down, random, and assign modes

SEQUENCER

• Polyphonic step sequencer with up to 64 steps and rests

EFFECTS

• Stereo analog distortion
• Dual, 24-bit, 48 kHz digital effects, including: reverb (room, hall, plate, spring), delay (full bandwidth digital delay and emulated bucket brigade and tape delays), chorus, flanger, phase shifters, and ring modulator
• Delay sync
• True bypass maintains fully analog signal path when digital effects are off

PERFORMANCE CONTROLS

• Full-sized, semi-weighted, 4-octave keyboard with velocity and aftertouch
• Backlit pitch and mod wheels
• Spring-loaded pitch wheel with selectable range per program (1 to 12 semitones up and down)
• Transpose controls for an 8-octave range
• Hold switch latches held notes on
• Polyphonic portamento
• Unison (monophonic) mode with configurable voice count, from one to all six voices, chord memory, and key modes
• Manual switch: when off, the front panel is live; what you see is what you hear

PATCH MEMORY

• 500 user and 500 factory programs in 10 banks of 100 programs each
• Direct program access, including single-button access to the current set of 10 programs