OK, here's the scoop: Richie, the electrician, completed the wiring of the new outlets to the room, as follows (BTW, I printed out this thread for him to read, and apart from a few questions about his competence, he explained to me why what he did met Code and was otherwise kosher): the 3 20 amp circuits are wired to the subpanel using #10 wire and each has a separate ground back to the subpanel. The subpanel ties into the main board at the 200amp breaker, but before any of the other breakers in the main panel. It shares the same ground as the main panel, but has an additional ground to earth in proximity to the house grounding rod. The subpanel is protected by its own 60 amp breaker, which then feeds the three 20 amp circuits. The subpanel is mounted adjacent to the main panel.
Since local supply houses did not have the Hubbell receptacles on hand, I bought a bunch of Porter's tweaked Hubbell receptacles.
Now, for the punchline. Perhaps a little less noise than when hooked up to the regular house outlets, but still suffering some grounding noise issues. Prior to installation of this new electrical subsystem, my best result was obtained by deriving all system power from the same set of outlets.(Remember, I don't draw a huge amount of current with this system).
Obviously, once I 'cheat' everything but the preamp, the grounding noise goes away, but I am still reluctant for safety reasons to lift the grounds on any of the equipment.
I have achieved quietude right now with the following arrangement- the Duo bass amps remain grounded through the 3 pin cord (Shunyata) plugged into a Hydra 2 which goes (with 3 pins) into one of the three new dedicated lines. (Each speaker has its own Hydra 2/Shunyata cord array, fully grounded, plugged into its own wall outlet right behind the speaker- both 'speaker ac' receptacles are on the same dedicated line- call that dedicated line "3").
The Lamm L2 line stage is plugged directly into the wall on dedicated circuit 2, no cheater. Ditto, the Steelhead phono preamp. Floating the ground of the STeelhead or not makes no discernible difference, so I have not cheated it.
The Audiopaxes are plugged into a Hydra 4/Anaconda which goes into dedicated circuit #1. Here, to get rid of the hum, I have to lift the ground on the amp cords going into the Hydra 4. (The Hydra 4 is using all 3 pins into the wall at dedicated circuit # 1 but viewing the Hydra as simply a wall receptacle extension, the amps really aren't
'grounded.')
I also tried plugging the Hydra 4/Audiopaxes (no cheater on the amp cords) into dedicated circuit #2, which powers the Lamm line stage, and no improvement.
I have hooked up the Granite Audio Ground Zero product, and have separate ground lines from the Duo amps, the Audiopaxes(cheated, as above), and the Steelhead all converging at the Ground Zero device. With some experimentation, this yielded a relatively quiet, hum free system, but if I ground the Ground Zero to a wall socket, using the supplied 'dummy' 3 pin plug, the hum is back.
For safety reasons, I'd still prefer to be able to avoid any cheaters. To sum up, right now, the only cheated plugs are on the Audiopax amps. (I assume that unplugging the Hydra 4 from the wall when I am not using the system makes no difference for safety purposes, since the amps are still connected to the rest of the system via the interconnect and speaker cables).
So, if you've hung in with me so far, it seems that there is almost no way around lifing the ground in this system somewhere to make it noise free. The grounding problem is an 'intercomponent' grounding difference, and not a bad ground from the wall. The grounding differential appears to be between the Audiopax amps and the amps in the subwoofers.
The only thing I didn't try was to also hook up the Duo subwoofer amps to the same dedicated circuit as the front end electronics- I could try that, which would mean the whole system is running on one 20 amp circuit- probably not a problem from a current draw perspective, but it would mean , if that worked, that I would have to have Richie rewire the outlets now on circuit 3 to tie into circuit 2 instead- I will test this temporarily before having him do that. It also means that having multiple dedicated lines for the same system is pointless, given the grounding differential between the circuits.(And, to the extent there is some subtle benefit to having more current on hand, despite the modest demands of my system, I am losing the benefit of that by forcing everything to feed off one 20 amp line).
With sincere apologies for the length of this post, I invite any thoughts or suggestions (:)!
