Gonk and Palmer,

thanks for your responses. Gonk, I think I probably have issues with each point you site. And, Palmer, thanks for the filter recommendation; I think I will buy one of these units.

I've also been told that local transformers can introduce this kind of hum and given I'm fifth from the transformer, I'm wondering if it isn't at issue, also, given the changeable state of the problem.

While I've been out of this game for the past ten years, the new and higher level of transparency introduces also more complexity and the need for care ... a double edge sword.

Anyway, again, thanks for the responses.

John