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DIY Roland GR-700 4x Memory Expansion

DIY Roland GR-700 4x Memory Expansion

Features and Specifications:

  • Expand patch memory from 128 patches to 320 (5 x 64 = 320)
  • Adds four selectable external memory banks of 64 patches each
  • Use either 1, 4-position, to pole rotary switch or 2 SPST switches to select banks

M-16C 4x Memory Expansion Using M-64C Memory Cartridge - 320 Patch Memory:

M-16C 4x Memory Expansion Using M-64C Memory Cartridge - 320 Patch Memory:

Summary:

The memory capacity of the Roland GR-700, and other synthesizers that use the Roland M-16C memory cartridge, can be easily expanded from one external bank of sounds, to four external banks of sounds by using a M-64C and a simple modification.

The M-64C has four times the memory capacity of the M-16C. Normally, plugging a M-64C into a Roland GR-700 does not add any additional memory capacity. The GR-700 will "see" the M-64C as if it is a M-16C, with a capacity of 64 sounds.

This modification changes the status of memory address lines A11 and A12. By alternately grounding A11 and A12, the M-64C has its memory divided into four equal sections. Each section will appear to be a separate M-16C cartridge to the Roland GR-700. This modification works for any Roland synthesizer that uses only the M-16C. So you can also use this modification with the Roland JX-3P, for example.

How-To:

This modification works by cutting control lines #13 and #16 on the M-16C memory cartridge slot (inside the GR-700) and adding a 2-pole 4-position switch, or two on/off SPST (single pole single throw) switches, and using a M-64C memory cartridge.

Use an X-Acto knife or Dremel tool to cut the tracings for control lines #13 and #16. Solder wires to the inner solder pads for control lines #13 and #16, and also attach a wires to control line #15, ground. When I installed this modification, I used a 2-pole 4-position switch ALPS rotary switch. Alternatively, you can use two on/off SPST (single pole single throw) switches. The four banks are created by alternatively grounding pins #13 and #16.

Memory Bank Diagram (Used with M-64C Cartridge):

Bank A B C D
Pin #13 N/C GND N/C GND
Pin #16 N/C N/C GND GND

If you refer to the above diagram, you will see that with both pins #13 and #16 grounded, the GR-700 addresses "Bank D." If you plug a M-64C into the GR-700 without this modification, this is the bank of the GR-700 will address.

With pin #13 only grounded, the GR-700 addresses "Bank B." With pin #16 only grounded, the GR-700 addresses "Bank C." With pin #13 and #16 unconnected, then the GR-700 is reading "Bank A."

This is actually kind of handy: I have copied sounds from a unmodified GR-700 to a M-64C as "Bank D" then inserted the M-64C into a modified GR-700, and loaded in the sounds to my GR-700's internal memory.

Links to more information:

Photos:

gr-700 memory epansion gr-700 memory epansion gr-700 memory epansion gr-700 memory epansion
Modified M-16C cartridge receptacle installed in Roland GR-700 Diagram showing wiring of the M-16C cartridge to four position ALPS switch Close up of ALPS switch. Note that the middle pin on the top has been cut. Wiring the ALP switch in process. Note the middle pin has been cut.
Click on any image to enlarge in new window.

GR-700 Memory Expansion