Why is a 1.5-2 volt AC signal on my Neutral line?

You have a ground loop problem between one or more units. Also if you have a separate line and breaker but use the same ground at the box, it is all still connected together. If you know this please forgive me but you must drive a new ground rod at least 8 feet away from the other ground or where the water pipe goes into the ground. This could be shorter or longer away depending on the soil; hard or soft - wet or dry, etc.! Back to the ground loop. Disconnect one unit at the time until the hum is gone. That is the one that has the difference of potential. Sometimes you can connect a wire between the two units, under chassis screws and solve the problem and sometimes you have to sell the problem and get something else. Ground loops are one of the hardest problems to fix. There is another way to fix or at least remove the noise but it takes a lot more electronic work. However, like said too already one of your rca's could have lost it's ground. With locking RCA's this happenings a lot more because the IC is pulled or heavy maybe and breaks the cheap little pin and hum! It does not matter if you are using that RCA's or not because the broken ground acts like a antenna for noise. Good luck!

Hum Gone!

I bought a ground loop isolator by Behringer - it is exceptional since there is negligeable signal loss and the signal quality is maintained

I understand the Jensen product is also very good

Thanks for the input

UPDATE: turns out NAIM only ties the neutral side to the ground in their source components - not at the amp.

The Ground Loop isolator mentioned above eliminated the additional hum introduced by the Pioneer DVD player.

But when I connected the "Ground" screw on the Phono stage to the ground screw on the power conditioner an eerie silence came over the entire system

The manual for the phono stage does not indicate whether this is good or bad practice, but it works and I did not have to mess with grounding component chassis - just used the terminals available.

Anyhow - all is now quiet - just very pure music - I even removed the ground loop isolator.

I am glad that we were able to pinpoint the problem as being due to a Ground Loop and help you solve it!