GCPH - hum when gain is turned to 2/3 o'clock

I own a GCPH phono stage and I am pretty happy with its performance and functionality, I use it directly with a power amplifier, however if I turn the gain control to 2/3 o’clock hum and noise can be clearly heard. I have disconnected the phono and the noise is still there.

Is there a way to eliminate this noise?

It is the ground wire connected from the board to the chassis. Send me an email I will show you how to eliminate this hum

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