July 2021
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Roland G-707 Hex Fuzz Upgrade

Roland G-707 Hex Fuzz Upgrade

Features and Specifications:

  • Add Hex Fuzz Output for Roland GR-300
  • Easy-to-find Parts
  • Maybe used with BX-13 series if Hex Fuzz output enabled

Modifications:

Hex Fuzz Card (Polydistortion) - UPDATED 2013-04-26:

Unlike the G-202/303/505 or 808, the Roland G-707 does not have a hex fuzz circuit. Nor does the Ibanez IMG2010, or the GK-1. However, if you have some basic soldering skills, you can make you own simplified hex fuzz circuit card to add the hex fuzz capability to the Roland G-707 or Ibanez IMG2010.

The hex fuzz circuit shown below is based on the hex fuzz found in the Roland G-202 guitar. To hear the hex fuzz sound, you need to use the guitar with the Roland GR-300. The GR-300 is the only synthesizer that actually uses the hex fuzz sound as part of its output options. The Roland GR-100 is a dedicated hex fuzz synthesizer, but the GR-100 uses the hex fuzz sound generated internally, and not the hex fuzz output from the guitar.

After my most recent installation of this hex fuzz card on a Roland GR-700, I found I got the best results using BAT46 diodes and I increased the output resistor from 120K to 220K. The BAT46 diodes are a bit more expensive than the generic 1N914 diodes I used before, but they provide a much more satisfying level of distortion.

Parts needed:

  • PC Board.
  • 6 - BAT46 Diodes.
  • 6 - 10K resistors.
  • 6 - 100K resistors.
  • 1 - 220K resistors.
  • 1 - 120 pF capacitor (ceramic)
  • TL082 Operational Amplifier and 8-pin socket (optional).
G-707 Hex Fuzz Modification G-707 Hex Fuzz Modification G-707 Hex Fuzz Modification
G-707 Hex Fuzz Modification G-707 Hex Fuzz Modification G-707 Hex Fuzz Modification
G-707 Hex Fuzz Modification G-707 Hex Fuzz Modification G-707 Hex Fuzz Modification
Click on any image for larger view.

I installed this circuit on a small PC board sold by Radio Shack. I soldered input wires directly to the individual string outputs directly on the 24-pin connector.

The value of the 220K resistor determines the output level of the circuit. The 120 pF capacitor determines the brightness of the circuit. You can build the circuit without the 120 pF capacitor, resulting in a bright, buzzy sound. You will notice that this circuit only uses 1/2 of the TL082 op-amp.