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. This synthesizer's filter aroused considerable interest at the time because it was the first to provide a sound different from 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

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 set A and B and are applied in series one after the other. Reverb is traditionally placed at the end of the chain, which is why 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 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 an LFO with 5 waveforms: 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 found in OB-6 are 4-stage (ADSR). The first is dedicated to the filter, the second to the VCA. The amplifier envelope was named by Tom as Loudness Envelope.

The Polyphonic Sequencer and Arpeggiator of the OB-6

The polyphonic sequencer allows storing a maximum of 64 steps and supports up to 6 notes simultaneously per step. While a sequence is playing, you can play over it 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 successions, and in the order in which we play the notes. Synchronizable to an external MIDI Clock or to the internal Master Clock with Tap Tempo (BPM control and display), the arpeggiator also provides 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, complete MIDI connectivity could not be missing, consisting of the classic triad (In, Out, and Thru) on five-pin DIN connectors 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 over USB connections (for example: Akai Pro MPC or Force). You can connect a footswitch-type Sustain pedal (¼” TS jack), 2 expression pedals (¼” TRS jack), one for volume and one for the filter cutoff, and a footswitch for managing the on/off of the sequencer to your OB-6. As audio outputs, we find two (L and R) ¼” TS jacks and a stereo headphone output (TRS) on a ¼” jack.

Controls and Memories of the Sequential OB-6

The panel features a potentiometer for each function and puts practically all OB-6 parameters within easy reach. 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.

Features of the Sequential OB-6

    
• 6-voice analog polyphonic synth
    
• Desktop Module Version
    
• 500 user and 500 factory programs
    
• 2 discrete VCOs per voice
    
• Continuously variable waveform
    
• Saw, variable width Pulse
    
• + Triangle 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
    
• 2-pole state-variable VCF (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 and 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 jacks)
    
• Headphone output (1/4" TRS stereo jack)
    
• 1 x 1/4′′ TS jack input for Sustain pedal
    
• 1 x 1/4′′ TRS jack input for expression pedal
    
• 1 x 1/4′′ TRS jack input for low-pass filter pedal
    
• 1 x 1/4” TS jack input for Sequencer/Arpeggiator pedal
    
• Dimensions and weight: 52x19.8x11.2cm; 5.9KG
    
• IEC connector for power cable
    
• Consumption: max 30 watts
    
• Walnut side panels and finish