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inside a Sequential Circuits Six-Trak
"The Six-Trak was released by Sequential Circuits around 1984 (Model 610).
It is a 6-voice, Polyphonic, Multitimbral, Programmable Synthesizer that has MIDI, a built in Sequencer, an Arpeggiator, and a 4-Octave (C-C) keyboard.
The Six-Trak was one of the first multitimbral MIDI instruments designed to be used with a computer with software that was available for the Commodore 64. The software allowed programming of the six voices and the sequencing.
Along with the DrumTraks drum machine, SCI claimed that with the software and this synth that it was a complete MIDI system.
Each voice can be programmed to any of the 100 internal patches and played as a separate monphonic synth. It can be played either by the external keyboard controller or an external sequencer as well.
The Curtis CEM) 3394 chips were used for each voice which contains one VCO, VCF, VCA, and LFO for each. The VCO has fine and course tuning, glide (portamento) as well as saw, triangle, and pulse (with pulse width modulation) waveforms.
Each Oscillator can be mixed with a noise generator as well and the filter section features controls for Cut-Off Frequency and Resonance.
You can also set the key follow modulation to full, off, or half.
The filter is also self-resonating and can be modulated by each oscillator.
Each voice contains an ADSR Envelope for each the VCO, VCF, and VCA.
The LFO can be routed to the VCO, VCA, and PWM and consist of such waveforms as square and triangle.
There is a single data entry knob used for programming and all the programming is done through menus. However, you can select the knob to control such things as frequency cut off and effect the filter as you play.
You can choose between Polyphonic (with portamento), Unison, and Stack modes (which allows each voice to be set to a different patch and played as one complex mono sound. Mono and Stack modes are selectible between single and multi-triggering modes as well.
The Arpeggiator can be selected as Up, Down, or Assignable (which plays the notes in the order that they were played).
The keyboard can also be split into three areas.
The Pitch-Wheel is fixed at a range of a Mjor 3rd up and a Minor 3rd down.
The Modulation-Wheel controls the LFO amount.
All of the sequences and patches can be backed up via MIDI
The Six-Trak features an 800 note sequencer and 100 patch locations.
The rear of the synth consists of MIDI IN and OUT, a stereo audio jack which doubles as a headphone jack, a footswitch for sustain, and an accessible fuse f it were to ever blow.
The overall size of the Six-Trak is 28"x12"x4 1/2" and weighs approximately 18 pounds."
"Vintage Sequential Circuits Co. Model 800 Sequencer in perfect working condition. It’s just been serviced and ready for the future. The service report is part of the sale as a proof of what’s been done.
via the seller: "I am selling this as non-working unit.It powers up.I think the problem is with the internal clock not working.There is a guy on You Tube who talks about this problem [possibly here, here, or here]. You can manually step through the events.All switches seam to be working .I don't have an analog keyboard anymore,so I can't input any notes or play anything out.I've taken a few pictures showing different numbers and lights on the display.These units are very rare..There were only less than 500 made.Mine is SN 072 .I also have the start/stop foot switch.This unit is also made for the US market (110v).Unlike the other unit listed from Japan that needs a power converter.I was the only owner.It sat in my smoke free personal studio for years.Then it was packed away.I might even have a photo copy of the circuit diagram somewhere that I will include if I find it.There is some scratches and nicks.But for as old as it is ,it's in good shape.No broken switches.All LED's light up.
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