anyone built GGG 6 band eq?

[347sixtyseven]

Hi guys,

Wondering if anyone has built the GGG eq successfully? I have found a few posts mentioning it but all seemed to say they had no luck with it.

Cheers

Gary

[Dave Simpson]

There's a few mods that need to be done to it so it work with other pedals on a shared power supply. It's also it's a little noisy, but it does sound pretty good though.

[347sixtyseven]

Thanks Dave,

Might throw one together and chase up the necessary mods.

Gary

[Dave Simpson]

Here's the mods. I'll save you a little time searching for them.

1. Disconnect point C from ground, and use point B as ground instead. That makes your negative battery terminal or negative supply voltage ground, so the pedal will work with others on the same supply. Point C is now your standard 4.5volt vref like you get in most FX pedals that use opamps.

2. Connect the input and output jack socket sleeves and the bottom of the final 10k resistor to point B, so that they are connected to the new ground. If you're using the GGG layout you can do this just by moving the jumper that normally connects those to point C to point B instead.

3. Flip the input cap so the positive end faces the 100k resistor and remove the 10uF cap in the feedback loop of the IC1b and replace it with a jumper. That will correctly bias the opamp now that it's referenced to 4.5volts instead of ground.

4. Install the 220K resistor immediately to the left of IC1, between pins 3 and 5. To tie the input of this opamp stage to ground, instead of letting it float.

[347sixtyseven]

Thanks heaps Dave,

Much appreciated

[Dave Simpson]

No problem, good luck with your build.