A guitar synthesizer, introduced by Roland in 1979 as a follow-on to the GR-500. The GR-300 voice architecture included two oscillators (not strictly VCOs, explained next paragraph) per string voice, and a paraphonic VCF and VCA, along with an LFO. A number of notable guitarists of the early 1980s took up the GR-300, including Pat Metheny, Robert Fripp, Adrian Belew, and Andy Summers.
Synth Architecture Edit
To address the tracking issues that discouraged some users of the GR-500, the GR-300 used a completely different method of frequency tracking. Instead of using pitch to voltage conversion, the signal from each guitar string was shaped into a pulse wave. This was then used to directly synchronize an oscillator using a circuit known as a "phase locked loop". This provided very fast, nearly instantaneous response to a played note. The oscillator was based on a conventional VCO sawtooth core, but the charging voltage for the integrating capacitor, instead of being driven by a control voltage, was set at a rather high constant value. This resulted in a more or less pure sawtooth wave at high frequencies; however, at lower frequencies, the integrating capacitor voltage reached the power supply voltage before the end of the cycle and was unable to charge any further. The result was that lower notes had the peaks clipped off of the waveform, resulting in a varying timbre between high and low notes. The mix of the six string signals went into an envelope follower that drove the paraphonic VCA, and could also modulate the VCF. A pitch variation allowed the second oscillator to be shifted up or down a maximum of one octave, relative to the first oscillator. There is an "A" and a "B" pitch interval control, which the performer can switch back and forth using a foot switch.
The tradeoff with this type of oscillator circuit is that it does not produce a control voltage corresponding to the frequency of the notes being played, which means that pitch information is not available to other components of the synth, or to an external entity. This means that, for instance, the VCF cannot track the pitch of a played note, nor can another synth be driven via a CV/Gate interface. This limits the timbral possibilities of the GR-300, a problem that many players noted after a while. However, since the guitar synth concept was still fairly new at the time, it did not significantly harm GR-300 sales, especially since performers appreciated the fast and accurate tracking.
An LFO could be routed to the pitch of the second oscillator, or to the VCF. An envelope generator could be routed to the VCF (not to the VCA). String select switches allowed the performer to cut any selected strings out of the synth circuit.
Roland offered a choice of four new guitars for the GR-300, all equipped with the hex pickup needed to drive the synth circuits, plus additional conventional pickups. All had the same set of controls and the same electronics (including a built-into-the-guitar hex fuzz circuit), except for different pickup configurations. The four models:
- G-505: A Stratocaster-style guitar with three single-coil pickups plus the hex pickup. It included a Fender-style vibrato bridge, and Fender-style 5-way switch for selecting among the conventional pickups. Construction was also similar to the Strat, with a bolt-on neck.
- G-202: The least expensive guitar of the four, in the same body style as the G-505, but with two humbucking pickups in place of the three single-coils, and replacing the vibrato bridge with a fixed bridge. Colors available were solid colors, as opposed to the stain finishes used on the other three guitars
- G-303: A guitar with a mild double-cutaway body shape, similar to Yamaha guitars of the era. Two humbucking pickups plus the hex pickup were provided, and a pickup selector switch was placed on the upper cutaway, Gibson-style.
- G-808: Same body shape and configuration as the G-303, but with neck-through-body construction, and high-end woods used. Regarded as the flagship guitar for the GR_300.
These guitars were not quite as control-festooned as the GS-500, the guitar made for the GR-500, and so they looked more like conventional guitars -- an important consideration for some performers, who did not necessarily want their audiences to realize that they were playing a guitar synth. Each guitar had four conventional-looking guitar knobs, two smaller knobs, and a function switch, in addition to whatever switching was provided for the conventional pickups. The four knobs controlled: tone for the conventional pickups, guitar/synth balance, master volume, and VCF cutoff frequency. The two smaller knobs controlled VCF resonance and LFO depth; the switch selected LFO routing. All of these except the guitar tone control worked by sending control signals to the synth. None of these guitars had the GS-500's infinite sustain feature; as a substitute, the synth had an onboard compressor that could be switched in and out via a foot switch.
All of the guitars were made by Fuji-gen Roland, a joint venture between Roland and the Japanese guitar manufacturer Fuji-gen Gakki, which also made guitars for Yamaha and Ibanez at the time. Although the GR-300 and its guitars used the same 24-pin cable and connector as the GR-500, there were some differences in signal routing on the cable. As a result, the four GR-300 guitars cannot be used with the GR-500 synth, nor can the GS-500 guitar be used with the GR-300, without modification.
The GR-100 was a guitar processor that contained most of the circuitry in the GR-300, less the oscillators. It was not billed as a synth but rather as an "electronic guitar". It used the same guitars as the GR-300; some were available with control knob labeling that corresponded to the GR-100's functions.
The GR-33B was Roland's first guitar synth targeted towards bass players. The circuitry was essentially the same as the GR-300, but optimized for bass. Two dedicated basses were offered. The G-33 had a single-coil conventional pickup, plus the quad pickup for the synth. It replaced the single tone control of the guitar with a two-band active equalizer. The G-88 used neck-through-body construction and high-end materials, but was otherwise the same.