It happens to all recordings that you play? Some recordings are bad and inherently have lots of sibilants. Try the recording you know that doesn't have it and confirm if the problem still exists.
Otherwise, the VTA could be too high (tonearm tail higher than cart) or loading is too high. My system can't take 47k loading that makes the whole sonic picture too sharp.
Otherwise, the VTA could be too high (tonearm tail higher than cart) or loading is too high. My system can't take 47k loading that makes the whole sonic picture too sharp.