FInally I have a noise issue

Got a 5M 1/8” (3mm) headphone jack to RCA lead.

When the sound is not playing on the iPad it has low buzz coming out of the speakers.
And I’ve almost convinced myself it is picking up RF.

Other PreAmp inputs are mouse quiet.

Should I wind a copper wire around the thing and attach it to the preamp ground as a test?
Or I suppose a properly shielded cable is what is used??