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Roland GS-500 Guitar Synthesizer Controller

Roland GS-500 Guitar Synthesizer Controller

Features and Specifications:

  • Body: Mahogany
  • Finish: Acrylic sunburst
  • Neck: Set maple neck
  • Fingerboard: Rosewood
  • Frets: 22
  • Bridge: Adjustable, Roland
  • Nut: Polycarbonate
  • Tuning machines: Gotoh
  • Pickups: Roland U-4000L Humbucker
  • Scale:24 3/4"
  • Truss Rod: Single, Adjustable
  • Neck Width: 1 11/16"
  • Body Width: 13 1/4"
  • Body Depth: 2"
  • Overall Length: 40"
  • Weight: 11 lbs 3 oz
Jeff Beck Roland GR-500
Jeff Beck and the Roland GR-500

Introduction to the Roland GS-500:

The Roland GS-500 is the dedicated guitar controller for the Roland GR-500 analog guitar synthesizer. Even with substantial parts of its body cut away for the installation of support electronics, the GS-500 weighs in at more than 11 pounds. The GS-500 has been described as having a honey burst finish, and it is a uniquely beautiful instrument.

The GS-500 marked the beginning of the partnership of the Roland Corporation with Fujigen, the Japanese builders of Ibanez, Greco, and ultimately Fender guitars in the land of the rising sun. Products built by Fujigen for the vintage Roland synthesizers would take the name of "Fuji Roland," a marking found on both guitars and synthesizers. The Fujigen website still features a picture of the GS-500, along with the claim of building the world's first guitar synthesizer.

Neal Schon
Neal Schon and the Roland GR-500

The retail price on the GS-500 was around $1,000 in 1977, which converted into today's dollars equates to an astonishing $4,300. So think of the GS-500 as being the equivalent of a high-end Paul Reed Smith guitar, or the Moog Guitar. Of course, there are as many styles of guitars as there are guitar players, but if you are a fan of vintage, weighty Les Paul guitars, you will enjoy playing the elegant GS-500.

The neck is around 42 - 43 mm, with a pleasing modern shape. The neck is somewhat between the slimmer G-303/808 guitars, and the chunkier G-505 guitar.

Jeff Baxter Roland GR-500
Jeff Baxter and the Roland GR-500

When I first picked up the GS-500, I wondered why Roland included the little three-way EQ toggle switch on the guitar. The owner's manual explains the switch has three sounds: "1", normal, full-range sound. "2" hard, low-cut sound, and "3", acoustic, slightly attenuated lows and highs. You can watch the video clips below and evaluate for yourself the sound of these three modes.

In any case, I did come to appreciate the value of this three-way toggle switch. The GS-500 has only one humbucking pickup, so there is no way to quickly switch guitar tones by changing pickups. But the three way equalizer toggle switch adds a quick way to access a variety of sounds. This is helpful, since the GS-500 has only one pickup. The second pickup position has been replaced by a very strong set of magnets, needed for the infinite sustain system.

In addition to the traditional volume and tone controls, you will notice the GS-500 has additional knobs to control the levels of the various synthesizer sections in the GR-500, plus a master volume control. The red LEDs in each section work with the volume controls on the guitar, indicating whether a section is on or off, with the brightness being an approximate indication of the output level.

Links to more information:
GS-500 Connectors
Click to enlarge.

Versions: Latching/Non-Latching 24-pin Connectors.

The early GR-500s are generally seen with the pin-type connectors, and they use the C-24B 24-pin cables with pin-type ends more commonly identified with the Ibanez 24-pin synths and the Korg Z3, though the Roland SCC-700 used the same connectors as well.

The later GR-500s switched to the locking ring connectors, the C-24D. These are the much more familiar locking ring cables sold with most of the GR-100, GR-300, and GR-700 systems.

Early 24-pin connector (top), later connector (bottom).

The Infinite Sustain System

GS-500 Sustain Patent Diagram
Sustainer Patent Diagram.
Click to enlarge.

One of the most interesting features of the GS-500 is the infinite sustain system. This is the general idea: two powerful magnets of opposite polarity are placed in the position where you would typically find the neck pickup. These two magnets are placed just outside the strings, creating a very strong magnetic field across the strings. This magnetic field is much, much stronger than the magnetic field typically created by guitar pickups. Like other sustainer systems, such as the Fernandes Sustainer, the neck position is used since it is easier to stimulate vibration in the middle of the string, than at the far end.

GS-500 Magnets
Magnetic assembly in the "neck" pickup position.
Click to enlarge.

The individual outputs of the hexaphonic synth pickup are greatly amplified, and sent to the unique GS-500 tailpiece. The frets in the GS-500 are grounded. When you fret a string, current now flows through the string. In effect you now have a current flowing through a metal wire in a strong magnetic field. According to Fleming's law, this will cause the wire to move in the magnetic field.

GS-500 Ground Wire
Ground wire for GS-500.
Click to enlarge.

This creates a feedback loop: the vibration is picked up by the hexaphonic pickup, then amplified, and the string is stimulated to continue to vibrate at the same frequency.

You can think of the sustainer as a "reverse" guitar pickup. In a normal guitar pickup, magnets in the pickup create the magnetic field. A coil of wire sits in this magnetic field, and the metal guitar string vibrating in the magnetic field induces current flow which is then amplified to create the sound of an electric guitar.

This system would be hard to retrofit to any guitar, especially when one considers the problem of grounding the frets. If the GR-500 required a fret job, would this ruin the infinite sustainer? I am not sure if there are enough GS-500/GR-500 systems out there with enough use to know for sure.

Plastic Rings in the Tailpiece, Plastic Saddles in the Bridge
GS-500 Plastic Saddles
Plastic saddles in the GS-500 bridge.
Click to enlarge.

Surprisingly, the GS-500 makes extensive use of plastic parts in the bridge and tailpiece to electrically insulate each string, to isolate the feedback signals used to drive each string. There are small plastic rings in the tailpiece, and the bridge in the GS-500 uses plastic saddles, identical to the plastic saddles used in some vintage Gibson guitars. I found an eBay auction for a 1965 Gibson Riviera ABR-1 bridge with plastic saddles, and there were various other vintage Gibson guitars, including SGs, Les Pauls, that used the plastic saddles as well.

There is nothing in the GR/GS-500 service manual about plastic saddles. The only GS-500 I have experience with had a non-stock, metal bridge. Once I realized the guitar should have an electrically isolating bridge, the clouds parted and the operation of the sustainer seemed much more obvious. And I realized now that all the old GS-500 photos I looked at showed white, plastic saddles. Upon further consideration, plastic saddles are not that uncommon in acoustic guitars, and many electric guitars use a plastic nut, which is functionally very similar to the bridge.

How does the infinite sustainer work in practice?

You can check out the demo below to see the infinite sustainer in use. Again, I have to note this: I did these demos with a GS-500 that had a replacement metal bridge! This was before an extensive discussion with Christian Deschamps and Carlos Najar revealed that the GS-500 should have a bridge with plastic saddles. Again, thanks guys for using the gr300 forum to share your knowledge, and to Patrick Phelps for the detailed GS-500 photos!

In short, the performance of the sustainer in the video demo is compromised, and the effect I achieved is in part due to sympathetic resonance in the notes of the chord I played. On the other hand, it does show the sustainer circuit is more robust than I had thought.

Because of the VCA circuits in the GR-500, one can be fooled into thinking the sustainer has engaged, because the envelope tends to hold a note at a steady volume before suddenly dropping off. You might think the sustainer is working, when in reality your are listening to the effects of the VCA. The GR-300 does this to some extent as well.

One final consideration: some players are concerned about pickups being placed too closely to strings, since the pickup's strong magnetic fields can inhibit the ability of a string to vibrate freely, limiting sustain. The magnets in the sustainer system surely effect the sound of the guitar, given the strength of the magnetic field is much stronger than conventional pickups.

Improving the Response of the Sustainer:

GR-500 user Christian Deschamps has come upon what appears to be a simple, practical way to improve the function of the sustainer in the GS-500 guitar controller: keep your frets clean! The sustainer requires current to flow from the frets through strings to operate, and after cleaning his frets, Christian reported the sustainer worked substantially better. Here is his remarks from the vintage Roland guitar synth forum:

"I noticed that the frets are not so shiny on my GS-500, so an unusual idea came to my mind that possibly my sustainer is faulty due to bad contacts on the fretboard.

What idea you asked?

OK, there it is.

I used a P320-grit sandpaper on the frets. Please note that I didn't remove strings during this process (I know I'm a bit lazy). I guess that a higher grade of sandpapers is better, because this operation caused light scratches on the wood finishes. The result is unbelievable!

The sustainer works great now!"


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GR-500 GS-500 Eight-Part Video Introduction:

01 - Introduction to the Roland GR-500

The Roland GR/GS-500 paraphonic guitar synthesizer system was introduced in 1977, and it laid the foundation for the very successful Roland vintage 24-pin guitar synthesizers, like the GR-300 and GR-700, that would follow a few years later. The GR/GS-500 uses the same 24-pin cable as the later synths, and many of the control voltages, string outputs, etc. are the same across all the synths. The different systems are not 100% compatible, but can be engineered to work together with a few modifications.

02 - GS-500 Guitar Synthesizer Controller

The GS-500 guitar synthesizer controller is a solid and hefty instrument. Even with substantial parts of the body cut away to accommodate the electronics, this guitar still weighs slightly more than 11 pounds.

The retail price on the GS-500 was somewhere around $1,000 in 1977, which translates into around $4,300 in today's currency. So think of the GS-500 as being in the Paul Reed Smith category of guitars, or the high-end Moog guitars, and not a mass-produced instrument.

03 - GS-500 Guitar Synthesizer Controller Electronics

The first thing I asked myself when I saw the GS-500 was why did Roland include the little three way toggle switch next to the tone control? The owners manual explains that the switch has three sounds: 1, or normal pickup output. Setting 2 is a hard, low-cut sound, and 3 is acoustic, slightly attenuated lows and highs. I will play the three modes, and you can decide how to describe them.

In any case, I appreciated that this simple toggle switch adds a variety of sounds to the GS-500, and I realized that this was really helpful, given that the guitar only has one pickup.

04 - GR-500 Polyensemble Section

The first synth section of the GR-300 is the polyensemble. In the polyensemble section, each string is processed through proprietary Roland wave shaping chips to produce a variety of sounds.

The Polyensemble has a three stage envelope, identical to the envelope generators in the bass and solo melody section. You have control over: attack, decay, and sustain. With it's polyphonic effects, and smooth envelope generator, the Polyensemble may be one of the most musical sections in the GR-500.

05 - GR-500 Bass Section

The bass section represents the first real, pitch to control voltage synthesis in the GR-500. Like the polysensemble, there are multiple voices: Percussion, soft and hard. For me, this translate to percussive effects similar to the percussion simulation on a vintage Hammond organ, the soft sound, which is like an upright bass, and the hard sound, calling to mind a pick bass. Like the polysensemble, there is a three stage envelope generator.

06 - GR-500 Solo Melody Section

The most ambitious section of the GR-500 is the Solo melody. The Solo Melody is built around a last-note played priority pitch to voltage monophonic synthesizer. There are two waveforms available, a 16' pulse width modulation wave, 8' pulse width modulation wave, and 8' saw tooth wave. The width, or duty cycle, of the pulse wave can be manually set, or controller by either the LFO or envelope generator. The Solo Melody has the same attack, decay, and sustain envelope generator as the bass and poly ensemble sections. In addition to processing the mono synth output, the -24 dB per octave solo melody filter can also process the polysensemble output.

07 - Roland GS-500 with BX-13-VX and Roland GR-55 and VG-99

This clip is a demo of the GS-500 used with a special BX-13-VX that I built specifically for the GS-500.

The External Synth volume control on the guitar controls the GK Synth volume. The Remote switch and the Portamento switch on the guitar work as GK S1 and S2 switches.

08 - Roland GR-500 GS-500 Performance Piece

In this demo I use all four sections of the GR/GS-500 independently and together: Bass, Polyensemble, Solo Melody, and Guitar. This clip is a demo of the GS-500 used with the GS-500.


Listen to "Artic Circles" a short GR-500 demo by Chuck Hammer using the sustain system.

Modifications: Using the GS-500 with the GR-700

GS-500 Plays GR-700

The GS-500 guitar synthesizer controller shares the same basic circuit configuration as the later vintage Roland 24-pin controllers such as the G-202/303/505/707 or G-808. A few simple modifications can make the GS-500 capable of playing the GR-700.

A quick look at the 24-pin chart shows the major problem is the lack of synthesizer volume control, pin #9. Pin #9 is used by the G-202/303, etc. while absent in the GS-500. Without receiving a control voltage on pin #9, the GR-700 will appear to work, while producing no sound at all! Depending on your ambition and level of soldering skills, there are a few ways to modify the GS-500.

First, thanks to Danny Rowlandson for the help with the pdf wiring diagrams and his willing experimentation. Danny and I exchanged emails in 2011 when he first came upon this configuration of using a GS-500 to play a GR-700. Danny also came up with the idea of adding a 7805 to power the infinite sustain system (more on this below!).

1) Quick Fix: Synth Volume Output. The quickest fix is to wire a 1K resistor from pin #1 (+15 volt power) to pin #9 (synth volume), plus a 50K resistor from pin #3 (ground) to pin #9 (synth volume) inside the GS-500. With this change, you can plug the GS-500 into a GR-700, etc. and get sound. Unfortunately, you will not be able to change the volume level, but you will get sound!

The next step is to wire a 150 ohm resistor from pin #1 (+15 volt power) to pin #8 (master volume). By making this change, you can use the controls on the GS-500 to vary synthesizer parameters, such as filter cutoff, etc.

This chart shows how the controls on the GS-500 map to the more contemporary controls with the Quick Fix:

Pin GS-500 GR-100, GR-300 GR-700
11 P. Ens Filter Cutoff Filter Cutoff
12 Bass Resonance Edit
13 S. Melody N/C N/C
14 Ext. Synth LFO Depth LFO Depth

2) Full GS-500 Modification for Driving GR-700: If you are confident in your soldering skills, and feeling ambitious, you can go further with the modifications to the GS-500. Please check out the pdf linked below. In this modification, a 7805 voltage regulator is added to the GS-500 guitar to generate the +5 volt power supply needed to drive the infinite sustain circuit. The controls on the guitar are slightly reassigned to produce both a master volume, and synthesizer volume command, plus more.

Finally, this full modification changes the function of the Portamento and Remote switch on the guitar to support the GR-100/300/700 mode switch, and provides an on/off switch for the infinite sustain.

This chart shows how the controls on the GS-500 with the full modification map to the more contemporary controls:

Pin GS-500 GR-100, GR-300 GR-700
11 P. Ens Filter Cutoff Filter Cutoff
12 Bass Resonance Edit
14 S. Melody LFO Depth LFO Depth
09 Ext. Synth Synth Volume Synth Volume
What about the GR-100 and GR-300?

You can basically follow the full modification to get full functionality with the GR-100/GR-300, but I recommend waiting before installing the 7805 voltage regulator if using the GR-100 or GR-300. This is because the GR-100 and GR-300 have a smaller power supply, and powering the infinite sustain may draw more current than the GR-100 or GR-300 can supply.

Magazine Advertising:

Announcing: The Roland Guitar Synthesizer Pick Any Sound Play Me A Rainbow Each String is an Orchestra Mind Blower
Click on any image for larger view.

1977 Japanese Brochure with Sample Patches:

Roland GR-500 Brochure Detail Pic Roland GR-500 Brochure Detail Pic Roland GR-500 Brochure Detail Pic Roland GR-500 Brochure Detail Pic
Roland GR-500 Brochure Detail Pic Roland GR-500 Brochure Detail Pic Roland GR-500 Brochure Detail Pic Roland GR-500 Brochure Detail Pic
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1977 Brochure - Paraphonic Guitar:

1977 Paraphonic Brochure Detail 1977 Paraphonic Brochure Detail 1977 Paraphonic Brochure Detail 1977 Paraphonic Brochure Detail
Click on any image for larger view.