Old Crow's Synth Shop: Maintaining the Yamaha CS-80

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Far back in the mists of ancient time, before microcomputers and their offspring of digital signal processors became the basis for modern synthesizer voicing, there existed a rich, sonic world comprised purely of analog waveform generators, filters, transient generators and amplifiers. This was the golden age of electronic music that began inconspicuously in the 1920s with the Theremin and evolved gradually into the transistor circuits that defined the first Moog modular synthesizer. After Wendy Carlos and Robert Moog showed the world what could be done with the quirky but operational hardware in the hands of a skilled musician with the 1966 release of Switched-On Bach, electronic music seemed to be the "in" thing of the fading 60s and most of the 70s. Not electronic as in the jangling techno beat and sampled-to-Pluto-and-back of the trance/dance/rave scene as is today, but a purer electronic, when the goal was to explore all of the sonic landscape with the synthesizer, from classical to atmospheric.

In the early 1970s, the concept of the rock concert was rapidly growing from the club-and-theatre circuit of the 1960s into the stadium and arena venue. With these musicians came the desire to bring the electronic sound on stage with them, a thing previously impossible due to the difficulty in transforming the studio synthesizer into a real-time performance instrument. Moog Music unveiled their Minimoog in 1971, and the rush was on. Fat leads and powerful basses made it to the stage, but still lacking in the minds of many performers was the polyphonic synthesizer that would complete the gap.

Moog, Korg, Yamaha (just to name a few) were well aware of the desire to get polyphony on stage. Moog had their Polymoog project underway, and Korg had the Delta/Sigma coming out, but Yamaha drew on their Electone organ engineering team to come up with the musician's polyphonic synthesizer. Taking 3 years to develop, Yamaha took the layout of the EX-42 triple-manual+pedalboard organ and fashioned a synthesizer--THE synthesizer of which arguably no equal has yet been seen in terms of performance potential: The Yamaha GX1.

Of course, the GX1 weighed half a tonne and listed at $60,000 (in 1976 dollars!), but the elite musicians of the day such as Keith Emerson and Stevie Wonder managed to bring them along on tour. Even so, the GX1 was known to be a R&D prototype of which about 70 machines were built, most never leaving Japan. The GX1 had discrete (individual transistors) circuits, which accounted for much of its bulk. Yamaha developed those circuits in discrete form and placed them in epoxy-filled 'potting boxes' to create pre-calibrated submodules. These modules are also found in the SY-1 and SY-2 solo synthesizers, as well as the CSY-1 and CSY-2 organs.

Update: In January 2004, the author managed to reverse-engineer several of these submodules and made an interesting discovery: they are not discrete versions of the IG-series chips Yamaha used in the CS series. They are different circuit topologies entirely. Plans are underway to open a new page on this site detailing what is actually in the submodules. Nevertheless, higher level concepts such as the dual voicing and realtime performance controls were tested on the GX1 before Yamaha advanced to the next phase of their performing keyboard plan: the CS-series.

The CS-series started with the CS-50 in 1976, a four-voice polyphonic keyboard that was the first to feature the integrated-circuit versions of their previously discrete oscillators, filters, amplifiers and envelope generators. Yamaha also introduced the pressure-sensitive keyboard, which had been previously been a custom-only feature on very few keyboards. Yamaha tested their new chipset with the CS-50 for a year while designing their real goals: the CS-60 and CS-80. The CS-60 is an eight-voice machine that uses the same circuitry as the CS-50 and adds the unique Yamaha pitch ribbon. The ribbon itself was nothing new, but the method Yamaha employed that allowed the "zero-point" to be wherever the ribbon was touched intially was an instant hit.

The CS-80, flagship of their new CS-series synthesizer line, represents Yamaha's attempt to cram as much of the GX1 into a single-manual keyboard as possible. More portable though still weighing in at 100kg, the CS-80 had dual eight-voice polyphony and a new feature never before attempted: polyphonic initial and aftertouch. The number of modulation controls assigned to working with the keyboard makes the CS-80 the best musician's keyboard ever created. Yamaha's own DX1 that arrived 7 years later as the flagship of the DX synthesizer line is the only keyboard that is equal in capability derived from the keyboard, and the DX1 owes this to the CS-80.

One man purchased a CS-80 in 1976 and that event changed his music from that moment on. The man's name is Vangelis, a Greek composer who rose to fame with his academy award-winning score to Chariots of Fire in 1981--composed mostly using the CS-80 and a piano. Vangelis was already working on at that time what is still considered to be one of the best film scores ever recorded, the soundtrack to director Ridley Scott's "Blade Runner", a film that in itself changed the way science-fiction films were made. The haunting, articulated notes that seem to permeate the smog of the film's future vision of Los Angeles, the rising swell of lush chords as a spinner takes off, the sultry lead and dark strings of the Blade Runner's Blues--this is the power of the CS-80, and why every CS-80 that yet exists in the 21st century deserves to live on.

Before delving into the secrets of the circuit boards that lie beneath the cover of the CS-80, here is my article on aging chips and capacitors, and what to do about them:

Tips for repairing vintage synthesizers

Repair and Calibration Information:

NEW Chip replacment list #1

Some Repairs for the CS-80

How to NOT follow the Yamaha literature (read this!)

CS-80 Manuals and Documentation:

The Secret CS Files on Juergen Haible's site

The CS-80 Adjustment Procedure (but see this first before following their instructions).

Service Bulletin for improving VCO stability in earlier models.

CS80 User Manual, Schematics/Block Diagrams and Service Manual

A Look at the CS-80

From the Outside

From the Inside

The CS-50 (and CS-60): Real CS Sound on a Budget

Crow's CS-80 / GX-1 Circuit Re-creations

GX-1 HP/LP Filters

Crow's CS-80 Filter, Now available for modular synthesizer systems.

The Original Prototype.

Scott Rider -- 0ldcr0w@0ldcr0ws.n3t