Phono stage hum

Does the Chinook run a  lot higher gain than the simaudio?
Is the gain adjustable on it?
Could account for some of the excess hum
Could be your expensive tt and wires are more sensitive to the gain difference than the cheaper tt ?

My older Teac tn300 never gave me any hum no matter what was in front or behind of it, My Nottingham on the other hand is a LOT more sensitive to things like cables, ac power lines, phono stage gain etc.

Call Manley tech support.  I had a SE version that developed a hum.  After various steps of troubleshooting they had me send it back.  They rotated one board 90 deg and solved the problem.

As noted above, the hum is isolated to the Manley, not the other units. Both channels. The most likely common point between the two channels is the power supply in the Manley. It could be a cap in the power supply or a different defective component in the ps. But just as a test, try reversing the power input to the unit, if that is possible in the Chinook. Might also try plugging all the electronics into the same wall outlet.  Maybe relocate the Chinook farther away from the cartridge to see if the cart is picking up hum from the phono stage.

I figured something interesting out - the hum is there even when the turn table power cord is unplugged.... but only if the TT RCAs are plugged into phono stage.

Strange that doesn’t happen with the other TT hooked up to the Manley.

Your TT RCAs need replacing - bad ground.