Sequential OB-6

The OB-6 is the result of collaboration between synth legends Dave Smith and Tom Oberheim. Inspired by the latter’s original SEM, the OB-6 features an all-analog signal path comprised of 6 voices (each with 2 VCOs, 1 sub oscillator), the classic Oberheim 2-pole filter (which can vary from lowpass, highpass, bandpass, and notch), a VCA section, and a 49-key keyboard spanning 4 octaves.

However, the OB-6 isn’t completely analogue, and for good reason. This hybrid beast features a dual digital effects section comprised of classic effects like Reverb, Delay, Flanger, Ring Modulation, and a Phase Shifter. The latter two effects are based on Oberheim’s original designs. Additionally, there is an X-Mod section, sourced from the filter envelope section and VCO2, which opens up the creative space for complex modulations and unorthodox sound design. These two sources can be sent to VCO1 parameters like frequency, shape, and pulse width, or they can be routed to the filter to control parameters like cutoff and mode.

OB-6 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