I agree that you should try a different amplifier with the speakers, and also perhaps a different CD player, though I think the odds are better with the amp.
I had a CJ preamp some years ago that ended up with a bad capacitor in the power supply that generated noise beyond my range of hearing. It was only when my son visited from college and pointed out the issue that I became aware and was able to fix it.
There is also the possibility that your amp is running out of power when you hear the distortion, but you really didn't say how loud you listen, or in how big of a room.
Lots of possibilities, but you just have to work through all of the components one at a time to find the cause.
I had a CJ preamp some years ago that ended up with a bad capacitor in the power supply that generated noise beyond my range of hearing. It was only when my son visited from college and pointed out the issue that I became aware and was able to fix it.
There is also the possibility that your amp is running out of power when you hear the distortion, but you really didn't say how loud you listen, or in how big of a room.
Lots of possibilities, but you just have to work through all of the components one at a time to find the cause.