Casio CZ/ VZ/ FZ - Pro Series

I recently purchased a CZ1, but unfortunately the sound from it is not as clean as my CZ101, which must be a fault since the CZ1 was so much more expensive. It sounds to me as if loud sound are getting slightly distorted, but in a kind of gnarly way (don't know exactly how to describe it!). This is with the chorus off. I expect some of the analog circuitry might be faulty. Has anyone ever had a problem like this before with the CZ1?

thanks