Squeak:

Reading what you've got going I'm guessing your whole house may have a problem with its grounding system, and probably squeaking by (no PUN here) by using the power company ground, which is a antenna of sorts. Don't know what your power company policy is, but here a report of power problems usually gets a free checkout from them. You should have a ground to a ground rod at your service entrance, or ground wire embedded in the foundation, or if a very old house grounding to a water pipe.
things to check for. Loose connections on ground at box and rod (tighten up all bare wire ground terminals in box) also have the power company retighten all lugs in the box and the meter base. (these loosen up from expansion/contraction from heat, and all copper to aluminium lugs get loose from use) Another possible for (poping crackling sound) loose connections from power company's transformer to meter, or a loose ground on the big transformer itsself.

Notice any noise, hiss,pops etc from T.V.'s stereo's etc? This would point to power or power ground problem.

I'm assuming yamaha has the 2000 grounded and has sheilded Rf (radio frequencies) producing areas.

Where their is noise problems Usually old tube amps etc. that love to amplify florecent lights etc. a seperated power source is required. I have one built in in my studio that handles everything on the stage at one end. I built this and it runs everything. All it is, is a 30 amp 220v (heavy duty) transformer that steps the power to 120v This cleans up the power very nicely and takes out about 90% of noise. I installed it in a large black box.

Just thought of something else you might try, havn't checked this out but seems like I recall the 2000 has a wall wart power transformer, If it does you might try using another one, maybe its got a leak in its insulation. Hope you find the problem and get it fixed, (very annoying to have good sound with a bug in it) ......Cheers......Pose