Roland GR-77B Programmable Analog Bass Guitar Synthesizer
Features and Specifications:
4 voice, Dual Oscillator Synth Engine Based on the Roland JX-8P
4 - Selectable Octave Settings for Each Oscillator, 2’, 4’, 8' and 16’
Choice of Square, Sawtooth, Pulse Waveform or Noise
Cross Modulation Between Oscillators
Frequency Modulation with Envelope and/or Modulation
VCF Low-Pass Filter with LFO, Envelope and Pitch Modulation
Variable High-Pass Filter
Dual Four Stage Envelope Generators
Low Frequency Oscillator for Vibrato Effects
Selectable Dynamic Control Over Pitch, Filter and Amplifier per string
Selectable Pitch Bend, Hold and Voice On/Off per String
Lush Analog Chorus Mode
Programming via foot switches or with optional PG-800 Programmer
Dimensions: 27 3/16" (W) 14 3/4" (D) 6 1/8" (H), 12 kg/26 lb. 8 oz.
Power Requirements: 45 watts
Introduction to the Roland GR-77B:
The GR-77B is the bass version of the classic Roland GR-700 guitar synthesizer. While the GR-77B is nearly identical to the GR-700 in form, the internal synth engine is based on the JX-8P, while the GR-700 is based on the JX-3P.
Guitar players struggle with the slower response time of the low strings on their guitar synthesizers, so the concept of a bass guitar synthesizer with even slower speeds of response was met with some skepticism, and rightfully so. While a few players have adapted the G-77 as a bass guitar, the GR-77B is the least heard of all the vintage Roland guitar synthesizer products.
To help with the speed issue the GR-77B has four processors, one for each string. Processor #4 served as both a driver for the string #4 synth section, and as the master interface. The remaining three processors were slaved to processor #4 for their synth parameter settings, while being dedicated to their respective strings for the synth output.
The GR-77B Synth Engine:
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Roland GR-77B |
Based on the JX-8P synthesizer engine, the GR-77B has two distinctive differences from the earlier GR-700 guitar synthesizer. While the GR-700 has only one envelope generator, the GR-77B adds a second ADSR four-stage envelope generator. With a second envelope generator, independent envelope based effects could be applied to pitch modulation, VCF and VCA.
The other very notable change was the use of the Roland IR3R05 VCA/VCF chip instead of the notorious 80017a chips which used the Roland IR3109 chip. Owners of the MKS-30/GR-700/JX-3P synths are well aware of the failures of the epoxy enclosed 80017a chip, but JX-8P/MKS-80/GR-77B owners fortunately do not have these problems.
In addition, there are various other changes, or improvements from the GR-700 to the GR-77B. While the GR-700 HOLD pedal only worked in a non-latching mode, requiring the player to keep a foot on the HOLD pedal to indefinitely sustain a note, the HOLD pedal on the GR-77B has a selectable, latching or non-latching mode. Also, the EDIT functions were relocated, with the top panel dynamics controls of the GR-700 now accessed through programming parameters. The MIDI implementation of the GR-77B is certainly deeper than the GR-700, probably reflecting the growing development of MIDI in the mid-eighties.
Finally, added to the top panel was an EDIT function to adjust the overall trigger level sensitivity, which is a nice addition to easily adjust the response of the GR-77B to different playing style.
Roland GR-77B Block Diagram (click to view on a new page).
GR-700 and GR-77B System Review and Details Guitar Player, June 1986.
AM8105 (Roland IR3R05) VCA/VCF chip clone with detailed information on the IR3R05.
Roland GR-77B Vintage Bass Synthesizer Photo Set at Flickr from MESonline
Roland G-77 Bass Synthesizer Controller
Schematics - Repairs - Service Bulletins:
There are no known service bulletins from Roland addressing any GR-77B problems.
The PG-800 programmer connects to the GR-77B synthesizer via a 6-pin DIN cable. These cables are easy to build if lost. They use a 6-pin DIN connector often used as a power plug. The pins are wired one-to-one, i.e. pin "1" to pin "1", etc.
6-pin connector for PG-200, PG-800, GR-700, GM-70, FC-100, FC-100 MKII.
Accessories:
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Roland US-2 with GR-33B, FV-200 and GR-77B. Thanks to Pablo Leocata for the photo! |
FV-200 volume pedal: The FV-200 volume pedal could be used to control the filter cutoff on all the vintage Roland synths, GR-100, GR-300, GR-33B, GR-77B and the GR-700. The FV-200 could also be used as a pitch pedal with the Roland GR-700 and GR-77B.
US-2 Unit Selector for controlling multiple vintage synthesizers.
M-16C Memory Cartridge: These handy-dandy little cartridges double the memory of many Roland devices. Used with a Roland GR-77B, patch memory goes from 64 to 128 patches. With a JX8P you add 32 more patches, and it can be used for synth patches on the JX-10 or for sequence memory!
More information on the Roland M-16C Memory Cartridge.
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PG-800 Programmer: Roland also made the PG-800 programmer to help program the GR-77B, JX-8P and MKS-70. Like other Roland programmers, the base is covered with a magnetic material to allow it to securely attach to the top of the GR-77B or the JX-8P synthesizer.
The PG-800 programmer connects to the GR-77B synthesizer via a 6-pin DIN cable. These cables are easy to build if lost. They use a 6-pin DIN connector often used as a power plug. The pins are wired one-to-one, i.e. pin "1" to pin "1", etc.
6-pin connector for PG-200, PG-800, GR-700, GM-70, FC-100, FC-100 MKII.
Roland PG-800 Service Manual Schematics.
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AB-700 GR Guitar System Case: For the heavy and bulky Roland GR-77B or GR-700, Roland made an aluminum case, the AB-700.
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Filter and Pitch Pedal:
On the rear of the GR-77B are filter and pitch pedal inputs. You can plug any volume pedal into this jack, and easily sweep the filter or change pitch. You will plug a standard guitar cable from the GR-77B filter or pitch pedal jack to the output of the volume pedal.
GR-77B Filter/Pitch Pedal Recommendation #1 - Korg EXP-2
My favorite pedal is the flexible, versatile Korg EXP-2. With a Korg EXP-2, you do not have to re-wire the pedal, since it also doubles as a volume pedal. Just plug a standard guitar cable from the GR-77B filter/pitch pedal jack to the output of the EXP-2 volume pedal jack, and you will get a wide, musical range of filter sweeps.
GR-77B Filter/Pitch Pedal Recommendation #2 - Behringer FCV-100
The Behringer FCV-100 is a pedal that can function as a dual, stereo volume pedal, or as a control voltage pedal with a 50K pot. However, the FCV-100 cannot be used directly with the GR-300, GR-77B or GR-700. Since the FCV-100 has an internal PC board, the easiest way to adapt the pedal for the GR-700 is to modify a TRS tip-ring-sleeve cable.
To make the FCV-100 compatible with the GR-77B, just
reverse the tip and ring wires on one end of a tip-ring-sleeve cable. The other end should be left unchanged. This will reverse the operation of the pedal, resulting in pedal up (dark, filter closed), pedal down (bright, filter opened), as shown in the YouTube clip. I have tested this with both a GR-300, and GR-700. It works with the GR-77B with either the filter or pitch input. It does not matter which end of the cable is plugged into the synth.
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Click on image to enlarge |
I would note that GR-300 user Joe Bartone, of the band Thelonius Dub, found that the FCV-100 did not hold up well on the gig. By the third gig, the rubber pad came off the pedal. Joe patiently bought some epoxy and took care of that problem...then the bottom of the pedal disconnected from the chassis. Not a big issue, but it meant constantly putting it back together every time he took it out for use. Finally, Joe reported that the pedal went "soft" meaning that it would tilt down when he took his foot off it. It does not stay in position like a quality pedal does. Taking Joe's remarks in hand, I would not give the FCV-100 a strong recommendation at this time.
