Hi, I've just pulled out my old AS500 from storage and noticed it gives quite a strong distortion effect across both speakers when it's on low volume. The distortion disappears when i increase the amount of amplification though(decrease the source volume and increase the amp power). I don't think this is a speaker issue (2x monitor BX2's) as i've checked their impedance and they have no distortion when i just increase the amplification with the same volume. I'm playing the music through the phono input and was wondering it might be from the phono pre amp, although should that happen over both outputs?? Also if it is this what's the best way to fix it? thanks!