Gosh, where to begin? I had the same problem with the JD9 but I'll come back to that ;--)
Almando, what kind of phonoamp are you using? And what kind of tonearm cables are you using to connect the cartridge/tonearm to the phonoamp -- by which I mean:
1. What make and model?
2. What length? The standard is 1.2 meter (or about 4 ft.)
3. What configuration/termination?
a.) DIN plug at the tonearm to RCA's at the phonoamp.
b.) RCA (junction box at TT) to RCA on phonoamp.
c.) XLR-to-XLR, or some combo of RCA and XLR?
e.) Separate ground wire?
Until I know what your wiring arrangement is, I can't comment further, other than to say you have some great equipment plus the fabulous Exactpower gear, so the noise has to be airborne and is most likely getting in through the cables (probably) between the TT and the phonoamp.
If it isn't the run of interconnect (between cartridge and phonoamp) then it could be that the gain in the Modwright is set too high. There could also be a redundant (extra, un-needed) ground connection between the turntable and the phonoamp, another between the tonearm and the phonoamp, possibly another in the TT between the tonearm and the TT chassis -- forming a big 'loop antenna'! Let me know.
I just bought a JD9 with all the upgrades, but it's going on AgoN this weekend. It's a nice little phonoamp, but I wanted a TUBE phonoamp (which it says it is on the faceplate!) but it is no such animal! It is a fully solid state phonoamp with three levels of gain using 3 pairs of Texas Instruments op-amps. It has a pair of 12AX7's right before the output, but they provide no gain. They are called "cathode followers, and operate at 'unity gain' -- bottom line: they can't provide the "signal-preserving" capabilities of tubes when they are used for the gain stages -- instead they add a sort of phony "tube warmth" to the output signal -- which isn't what I was looking for ;--((