Did you check the tonearm cables at the cartridge, which is where you most likely have a loose connection or broken wire, then back to the RCA outputs, be they captive cable or jacks on the table. These tiny, delicate wires are the most likely culprit for noise of all types. If you did check them, do it again, took me three times to find the loose connection, but then I'm an idiot, or at least thought so when I finally found it. Second, do you use shielded cable from the table? Might be RFI from a local radio tower or an appliance in your house cycling on and off, think refrigerator or AC unit. The only shielded cable I had around the house was a pair of Monster Cable 550i, wasn't the issue, but found they sound really nice, pleasant surprise.