The Filter of the Sequential OB-6

The OB-6's filter is analog, two-pole (12db per octave), state-variable with Low-pass, High-pass, Notch, and Band-pass. A filter inspired by the S.E.M. (Synthesizer Expander Module) project, which was the first synthesizer created by Tom Oberheim in 1974. The filter of this synthesizer aroused considerable interest at the time because it was the first to give a different sound compared to others on the market (Moog and Arp). Even today, the sound of this filter is re-proposed by many manufacturers of modular and keyboard synthesizers.

The effects of the Sequential OB-6

The OB-6 is equipped with two high-quality Digital Effects. Reverbs, delays (standard and BBD), chorus, flanger, phase shifter, and faithful reproductions of Tom Oberheim's ring modulator. Both have a 24 bit/48kHz resolution and with the true-bypass function, they guarantee the purity of the analog path. The effects are divided into sets A and B and are applied in series one after the other. Reverb is traditionally placed at the end of the chain, and for this reason, this effect is only found in set B. 

The Modulations of the OB-6

Sequential OB-6 has a modulation section called X-mod. Many of the most famous sounds of the OB series were created precisely with this section. The modulation sources are the filter envelope and oscillator 2, both with bipolar control. Destinations include oscillator 1 frequency, oscillator 1 waveform, oscillator 1 pulse width, filter Cut-Off, and filter mode: LP, HP, Notch, and BP.  In OB-6 we find a LFO with 5 waves: sine, sawtooth, rev saw, square, random. A sixth "hidden" one can be created by choosing Random and setting the frequency speed to maximum. This will create a White Noise-style waveform. The 2 envelopes we find in OB-6 are 4-stage (ADSR). The first is dedicated to the filter, the second to the VCA. The amplifier envelope was named Loudness Envelope by Tom.

The polyphonic sequencer and arpeggiator of OB-6

The polyphonic sequencer allows for the storage of up to 64 steps and supports up to 6 simultaneous notes per step. While a sequence is playing, you can play along with the rest of the available polyphony. You can create polyphonic sequences and synchronize them with an external MIDI clock. The programmable arpeggiator of the Sequential OB-6 can be configured in the classic Up, Down, Up + Down, Random progressions, and in the order in which the notes are played by us. Synchronizable to the external MIDI Clock or to the internal Master Clock with Tap Tempo (BPM control and display), the arpeggiator also provides the configurable Re-latch and Sustain functions. The notes generated by the arpeggiator or sequencer can be transmitted to the MIDI OUT; through the dedicated Global setting, we can decide whether to send them both via DIN and via USB, or only to one of the two options.

The connections of the Sequential OB-6

As in all instruments designed by Dave Smith, a complete MIDI connectivity could not be missing, consisting of the classic triad (In, Out, and Thru) on 5-pin DIN and a class-compliant USB type B port (no drivers needed) for bidirectional communication with your PC or Mac computer, or with another instrument that supports MIDI connections via USB (for example: Akai Pro MPC or Force). To your OB-6 you can connect a Footswitch type Sustain pedal (¼” TS jack), 2 expression pedals (¼” TRS jack), one for volume and one for filter cutoff, and a footswitch for managing the on/off of the sequencer. As audio outputs, we find two (L and R) ¼” TS jacks and a stereo headphone output (TRS) on a ¼” jack.

Keyboard controls and memories of the Sequential OB-6

The panel features a potentiometer for each function and puts virtually all OB-6 parameters at your fingertips. 500 permanent factory programs and 500 rewritable user programs are included. Pressing the Manual button enables live panel mode, where the OB-6's sound switches to the current front panel settings. In this state, what you see is what you hear. All the analog sonic power of the Sequential OB6 is easily playable from its four-octave semi-weighted keyboard with programmable velocity and aftertouch, making it perfect for both stage and recording studio.

Features of the Sequential OB-6

    
• 6-voice polyphonic analog synth
    
• 4-octave semi-weighted keyboard
    
• Velocity and aftertouch sensitive (mono)
    
• Backlit Pitch and Mod Wheels
    
• 500 user and 500 factory programs
    
• 2 discrete VCOs per voice
    
• Continuously variable waveform
    
• Saw, variable width Pulse
    
• + Triangular on oscillator 2
    
• Pulse width on each oscillator
    
• Hard Sync
    
• Square wave sub-oscillator
    
• Low Freq mode (osc 2)
    
• Keyboard Tracking on/off (osc 2)
    
• Unison with Chord Memory
    
• Poly-Chain
    
• VCF 2-pole state variable (LP, HP, Notch, BP)
    
• 1 LFO, 2 ADSR Envelopes
    
• X-Mod Modulation Matrix
    
• Glide
    
• 64-step Polyphonic Sequencer
    
• Programmable Arpeggiator
    
• 2 digital multi-effects set A set B
    
• Analog Distortion
    
• True-bypass
    
• Clock: Master (Tap Tempo), external MIDI
    
• MIDI: In, Out and Thru DIN, USB type B
    
• Main stereo output (2 x 1/4'' TS jack)
    
• Headphone output (1/4" TRS stereo jack)
    
• 1 1/4'' TS jack input for Sustain pedal
    
• 1 1/4'' TRS jack input for expression pedal
    
• 1 1/4'' TRS jack input for low-pass filter pedal
    
• 1 1/4” TS jack input for Sequencer/Arpeggiator pedal
    
• Dimensions and weight: 80.7x32.3x11.7cm; 9.5 kg
    
• IEC connector for power cable
    
• Consumption: max 30 watts
    
• Walnut side panels and finish