Hi Al - that is an interesting explanation, though I am not sure how the cause you describe would result in the effects I heard. I would think the cause you are describing would result in much more audible distortions, but perhaps not. The effects I experienced were more like a removal of too much information, if that makes sense. Perhaps the next time my brother comes up, I will experiment with plugging the TT-PSU into the conditioner as well, and see if that makes any difference. He doesn't have a separate power supply to his turntable.
As for the harshness definitions, I would not equate harshness solely with distortion. As Mr. T says, distortion is not necessarily unpleasant. Acousticians use the term distortion to describe many different types of phenomena, some of which are positive effects. I would also agree with his second definition, though this is certainly subjective, as he says. Many CD players I have heard have this "overly analytical" quality - to take an orchestral example, one may be able to clearly pick out every instrument on the stage, but the sense of how the combination of all of them sound out in the hall is completely lost. Losing the forest for the trees, so to speak. When the ambient noise, especially the warmth, of the original concert hall is taken away or lost in this fashion, the resulting sonority is certainly colder and could often be described as harsh.
As for the harshness definitions, I would not equate harshness solely with distortion. As Mr. T says, distortion is not necessarily unpleasant. Acousticians use the term distortion to describe many different types of phenomena, some of which are positive effects. I would also agree with his second definition, though this is certainly subjective, as he says. Many CD players I have heard have this "overly analytical" quality - to take an orchestral example, one may be able to clearly pick out every instrument on the stage, but the sense of how the combination of all of them sound out in the hall is completely lost. Losing the forest for the trees, so to speak. When the ambient noise, especially the warmth, of the original concert hall is taken away or lost in this fashion, the resulting sonority is certainly colder and could often be described as harsh.