I think it is. There is a wire from the turntable ground, to the sprout100 ground.
Grounding is a mystery I’ve never quite figured out. (how can a car be grounded when it is on rubber tires?)
Is my plug grounded, is my housing circuit grounded, is there copper rod sunk into the soil around my house, is the chemistry/moisture content of my soil conducive to grounding ??
Yes, the cables from the Fluance are two RCAs and a ground. The three are attached appropriately on the turntable, and then again attached at the back of the Sprout100.
Are one of the TT cables touching or crossing to close to a power cord? Also check to make sure all of the leads from the tonearm to the cartridge are properly seated.
I’m going to look forward to a follow-up as well. I’ve encountered a similar problem in a different category of component (and different manufacturer). A tone that sounds like it is pure, in my case in the upper midband. Long story short, it was traced to a switching power supply that I was informed has a history of occasionally becoming unstable. Even in linear power supplies, some linear regulators can resonate if not properly compensated or the components in the compensation loop have drifted too far due to aging.
Whether it actually corrupts the output can depend on the internal routing of the component. It was a fascinating lesson learned.