Distorted sound when volume is above 50%

[filipetolhuizen]

Hello,
A few months after I bought my B&W second-handed, the sound started to come out distorted, specially when using external speakers. This started to happen the day after I put a G4 ZIF module on it (original from a G4 PCI Graphics, aka Yikes!). Putting back the G3 did not fix this. It only happens when the main volume is above 50%. Do you have any ideas what could be causing this? It seems to be fine when using the internal speaker.