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Sunday, January 21st, 2018 12:17 am

Synth Glossary

A Low Frequency Oscillator. It is similar to a normal oscillator except that it outputs very low frequencies (very slow waves) and is used as a control input into another part of the synth. Examples of its use are to create vibrato or tremolo effects....


The CS-80 was first produced in 1977 as a commercial version of the larger and more elaborate GX-1. It was popularized in the late 70's and early 80's by a number of pop supergroups, including Paul McCartney and Wings (London Town), Electric Light Orchestra (Discovery) and Toto (Toto IV). The instrument's large physical dimensions (47.5 X 12 X 27 inches, and a hefty 220 pounds, or 100kg) and excessive price ($6900, or ?) probably limited its commercial success as it was forced to compete with smaller less expensive synthesizers like the Korg Trident and Sequential Circuits Prophet 5.

The CS-80 is much like having two 8-voice synthesizers layered together (a total of 16 oscillators!) and connected to a single velocity-sensitive, 5-octave, 61-note (C-C), semi- weighted-action keyboard. It features a completely analog voice structure. Each voice has a single VCO, both a high-pass filter and low-pass filter with resonance on both, and separate envelope generators for both the VCF and the VCA. The main control panel of the CS-80 slants forward, making room for a multitude of circuit boards underneath along the back of the synth. The main control panel features 3 rows of knobs and sliders. The first one (directly above the keyboard) is for general assignment and voice setup, the upper two rows are for the voice architecture of each of the two available patches. Each of those rows gives you control over a single set of 8 voices (a single layer of the total sound).

Voice Architecture
Each voice includes one VCO, a filter section, and a VCA section, along with four additional sliders controlling its response to velocity and aftertouch. Velocity can be used to control the volume, filter cutoff, and pitch-bend envelope. The pressure can be used to control volume, filter cutoff, Pulse-Width-Modulation LFOs, the main LFOs, and the main LFO speed. The VCO section features a choice of sawtooth, square and sine waveforms, as well as a noise source. There are on/off switches for both the square and sawtooth waveforms and a slider for the noise amount. Pulse-Width Modulation is available with its own LFO. There are sliders for the PWM's LFO speed, the amount of modulation, and the initial Pulse Width setting (from 50% to 90%). The VCO sine wave output is mixed into the patch after the VCF (before the VCA) and is never affected by the VCF setting or the Pulse Width settings. The filter section features both high- and low-Pass filters. Both have sliders for cut-off frequency and resonance. Neither can self-oscillate. The filter section features its own envelope generator, an ADR (attack, decay, release). Both high- and low-pass filters are affected the same way by the envelope generator. There are sliders for Initial Level, Attack Level, Attack Time, Decay Time, and Release Time. Just how these five sliders interact to crest an envelope takes some getting used to. The Initial Level slider does set the initial level of the envelope. However, the higher you set it, the less harmonics are present in the sound (which doesn't quite make much sense). When set in a high position it can be used to create somewhat of a sustain sound, since the decay will not go back to zero. The filters are still reportedly very musical. Their 12dB/octave slopes have a charming character, different than a moog filter, but still capable of doing rich bass sounds (which are enhanced by bringing in the VCO's sine wave after the filter section). The VCA section features a separate slider for the output of the VCF and for the sine wave output of the VCO. The VCA has its own ADSR (attack, decay, sustain, release) envelope generator, with slider for each and another one for overall level. The VCA and VCF envelopes both have a very fast available attack time of (1ms). However, longest attack time available is only 1 second. The release/decay times on both of these envelopes had a range of 10ms to 10 seconds.

Global Modulation & Control
The control/modulation section of the CS-80 features a coarse/fine tuning knob, tuning octave switches, the ring modulation section, the sub-oscillator (Yamaha's confusingly named LFO) section, resonance and brilliance sliders, buttons for patch selection, global controls for velocity and aftertouch response (this is in addition to the velocity and aftertouch controls on each of the patch parameters), and a main volume knob. The control settings here affect both patch/layers equally.

The tuning knob is a medium sized center-dented knob with a smaller fine-tuning knob sticking out of the middle of it (not the best of design ideas). It affects both layers. There is an additional knob that detunes the second bank from the first. The volume of each layer can also be adjusted. The CS-80, unfortunately, does not come with a pitch wheel. However, it has a quite a good alternative, the pitch ribbon (see below). It is possible to use the tuning knob as a pitch wheel. However, after having mastered the pitch ribbon, most performers use it exclusively. There are two slider switcher for setting the octave of each layer. Each of the two voice-layers can be set at 2', 2 2/3', 4', 5', 5 1/3, 8', and 16'.

The Ring Modulation section is quite elaborate, with sliders for modulation, speed, depth, attack time, and decay time. Modulation controls how much of the ring-mod signal is present in the sound compared to the original signal. Speed determines the basic frequency of the modulation signal. The depth, attack time, and decay sliders make up a simple AR envelope generator for controlling the frequency of the modulation signal ("speed"). The depth slider sets the maximum frequency reached, and the attack and decay sliders set how long it takes the modulation to speed up to its maximum frequency and how long it takes to slow down again. No other synth manufacturer has implemented a ring mod section in quite the same way. This is a part of the CS series' signature sound.

The LFO section, confusingly named "sub-oscillator", is switchable between Sine wave, Sawtooth waves (up or down), Square waves, noise source, and the external audio input signal. There are controls for speed and three sliders controlling amount sent to the VCO, VCF and VCA. Unfortunately, the single LFO affects both patches equally. This is one of the first things that a CS-80 user gets modified. The speed of the LFO is fast enough for some nice FM effects. Patch selection is quite straight forward. There are 14 available patches for each layer. Eleven of these are fixed, short of changing resistors on an internal board (actually not very hard). The other three buttons choose user defined patches. One button chooses the front-panel knobs (one set for each layer). The other two choose the programmable presets located in a small compartment under a cover in the upper left corner of the main control panel (to the left of the two main patch rows). These are 4 (two for each layer) sets of miniature sliders that are under a fold-up panel These four patches are "stored" by minisliders . . (Yes, even the memory is analog!) Here you will find four complete duplicate representations of a single patch, with sliders for the VCO, VCF, and VCA.

So in all there are 22 fixed presets (11 for each layer) and 6 user programmable sounds (3 for each layer). These are arranged on two rows of 14 square push-buttons. The presets are as follows: String 1-4, Brass 1-3, Flute, Electric Piano, Bass, Clavichord 1-2, Harpsichord 1-2, Organ 1-2, Guitar 1-2, and Funky 1-4. Each button lights up when selected. In addition to global control over resonance and brilliance, there are also two sets of global sliders that set the relative volume and brilliance of each end of the keyboard. This allows you to scale the filter and the VCA in both a positive slope or negative slope across the keyboard (quite useful).

The pitch ribbon sits directly above the keyboard. Unlike the Moog pitch ribbon (see the Micromoog or the Moog Liberation), which has a specific point for the center of pitch, the Yamaha ribbon uses wherever you first put your finger as the center pitch and allows you to slide up or down from that point on the ribbon. Or you can hold one finger down and tap another for hammer-trill effects. One cool thing about the pitch ribbon is that bending up gives you a range of about an octave while bending down gives you practically infinite octaves. (Down to zero hertz!) Other polysynths from the period can't do this because they have exponential VCOs, while the Yamaha's are linear.

To the left of the keyboard are additional controls for Sustain, Portamento/Glissando, Chorus/Tremolo, and two buttons controlling the footpedal response. The sustain selector switches between two types of sustain (which is not "sustain" as we know it, but rather affects envelope release). The first setting (I) lets a note decay normally. What is very cool is the second (II) sustain mode . In most synths, you can't have a long release on a polyphonic lead sound because you end up with a blur of notes. In sustain mode II hitting a new key, after letting go of all keys, kills sustaining notes. This lets you play sustained chords and leads together, an effect unknown to any other synth. Sustain can also be turned off and on via a foot-switch (much like a piano's sustain pedal).

The Portamento/Glissando switch allow you to select between the two effects. There is also an amount slider. The portamento is polyphonic and can also be switched from a foot pedal. Also in this section is the chorus/tremolo unit that can give various stereo chorus and Leslie- type effects, with a switch that allows you to select between the two effects and knobs for speed and depth. The effects are a bit noisy but very analog sounding and warm. The CS-80 comes equipped with inputs for both a switch and a footpedal controller (like an organ volume pedal). There is a slider controlling the footpedal range and a switch that allows you to select between "Exp" (volume) and "Exp Wah" (volume and filter cutoff). (Note: There is rumored to have been an additional selection planned but not implemented for just "Wah".

According to The A-Z of Analogue Synthesizers, by Peter Forrest "Yamaha were certainly in a hurry to get the CS-80 out there to dominate the potentially huge pro polysynth market: the first edition of the service manual has a lot of hand-drawn pages, including the main panel layout. Interestingly, there was a third button originally planned underneath the Exp/Exp Wah buttons: the legend [in the manual] has been scribbled out, but it was probably Wah. Wonder why they didn't implement something that would have been logical and useful."

Built Like a...
The CS-80 does have high quality sliders and knobs. The sliders are said to be "smooth, chunky, and just great to tweak." They're also color coded: green for general filter characteristics, red for filter resonance, white for pitch, grey for volume, yellow for sustain, and black for other functions. Although this color scheme helps, it does not make it in any way an "intuitive" synth. It does take a while to get used to which sliders do what (even for an experienced synthesist) and which way is maximum and minimum on allot of sliders and levers. Many of the performance controls have a drastic effect on the presets and must be set carefully before playing.

On the back panel are the outputs: Left, General, and Right (all unbalanced jacks). There is a switch to choose between high and low output levels. There are 1/4-inch jacks for the foot controller and pedal switch, and an External input, with a knob to adjust the input level. Unfortunately there are not CV/gate inputs. Installing Midi is said to be possible, but a bit expensive.

The CS-80 keyboard is built into a heavy plywood case covered in tolex with chrome corners. It came with a hard semi-flightcase top and a "very clunky chrome stand", which was fortunate because of its weight (around 220 pounds). Other accessories available included a clear plexiglass music stand, foot controller, footpedal, detachable casters for the case, a tube of Yamaha Key Cleaner and a leather case (presumable to stow the music stand and all of the accessories when they are not in use).

The Yamaha excels in creating a playing environment that allows you to tune the CS80 to react lively to your playing style and habits. It is simply a joy to play, which is one of the reasons why it has developed a loyal following. However, there are some drawbacks to owning a CS-80.

"Weight wasn't the only hassle inherent in the CS-80; like many analog synths, its oscillators tended to drift in pitch. 'The tuning was stable for about 20 minutes, and that's on a good one,' [Richard] Luebbing [a CS-80 expert with David L. Abell, Inc., in Los Angeles, California] claims. 'There were problems with air circulation inside the unit. Cooling wasn't the same for all of the oscillator cards, so they would drift at different rates.' "According to [Luebbing], this air circulation problem made the tuning process ugly. 'You couldn't keep the lid open for more than a minute -- preferably 30 seconds -- when making an adjustment, because the interior temperature would drop. You had to prop the lid open with a pencil, reach in, tweak a trim pot, close the lid, and let the temperature stabilize for about three minutes. I had a little egg timer and two digital thermometers that would tell me what the internal temperature was above the ventilation grills. Whenever the temperature started to fluctuate, I would notice that my tuning would not be accurate.' "As you can imagine, tuning the CS-80 wasn't much fun. It was both lengthy and expensive. 'My procedure took three days and I charged $300. Most of the synths I saw came in on a periodic basis. They were owned by professionals like [L.A. session ace] Ralph Grierson. Tuning is a religion with him; he would bring his in every two weeks.' "Three hundred bucks? Maybe tuning was covered under the CS-80's warranty. 'No,' Luebbing admits, 'but we'd get you in the ballpark the first couple of times for free.' "Even the CS-80's case design had a detrimental effect on tuning. 'There were four casters that could be inserted into holes on the CS-80's back panel and lid,' Luebbing explains, 'so that you could roll it around like a huge suitcase. Unfortunately, the way the tuning trimmers were located, if you moved the CS-80 the way the manufacturer intended, the vibration was in the same plane as the trimmer adjustment. The CS-80 could be nicely in tune, and then the roadies would come, slam it down on the floor, and bounce it all the way to wherever it was going, and all the trimmers would drop into another position. Changing the trimmers themselves didn't help, because they were so sensitive. At their maximum, they required maybe a tenth of a degree turn to vary the tuning over several semitones.' For those CS- 80's to be transported to gigs or from his shop back to the owner, Luebbing insisted on hiring a cartage company that would 'do things my way and move the CS-80 in a horizontal position, which helped a good deal.'

"To combat the tuning problems, technicians tried various strategies, such as applying drops of fingernail polish to hold the trimmers still and installing internal cooling fans for improved air circulation. One of Luebbing's tactics really went beyond the ordinary. 'It involved the installation of a heat pipe, a fluid-filled copper tube, purchased from Edmund Scientific in New Jersey for about $70. There was less than a quarter-degree temperature change from one end to the other. I soldered a tab from each oscillator chip to the tube, and it would tend to keep them at the same temperature. Garth Hudson [of The Band] was the only CS-80 owner experimentally oriented enough to give it a try. Subject to its limitations, it did what it was supposed to do. Garth toured with that CS-80 up and down the East Coast. Then he brought it back about a year and a half later, and it was still tuned pretty well. Unfortunately, it was stolen when he was in New York, and we never heard from it again.' "Luebbing concedes that, in the proper environment, the CS-80's tuning 'actually could be made reasonably stable. If I give it a good in-studio tuning, it will be serviceable through a couple of sessions. If it isn't moved around and it's kept powered up and hot in a cool environment, it'll stay pretty well.' For that reason, Luebbing now insists on tuning a CS-80 in its habitat -- the studio. In his opinion, road use is out of the question.

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