My G-System gives an unwanted noise when turning on any modulation effect. What should I do?
First I suggest to verify each one of your cables is working properly. Take care to move away audio cables from power cables. If you are using other effect pedals in addition to your G-System, try using the G-System's integrated power supplies. There are 4 power supplies outlets available on the G-System.
Try to power your G-System in another main power socket, if possible in another main power circuit than your amplifier. If you use your G-System with other pedals, try your G-System alone, only with your amplifier.
IMPORTANT: If you use a tube amp, try to replace the preamp tubes one by one. The excessive noise and squealing should go away. Then, if you notice a clear improvement, the remaining noise can nicely be handled using the noise gate on the G-System.