All you can do is what anyone does with a noise problem, keep trying until you get lucky and find the source. In general terms, all the wire from the interconnect to the arm and cartridge and all the way until it gets inside the phono stage is one big antenna. That's always the case but we don't usually notice because if the connections are all uniformly good the noise is kind of random white noise and low level. Anything other than a perfect connection acts like a tuner and if it tunes to where there's a radio station, this is what you get.
Probably if you move the interconnect while connected and volume on you will hear it change. If you're lucky it can be eliminated that easily. If not its just down to trying lots of things. Clean all connections. Including grounds, and not just the RCA going in but going out, and AC. Check phono pins. Tear aluminum foil into strips, wrap around the IC. Try another IC. No one knows what it will be so try whatever's easiest first.
Probably if you move the interconnect while connected and volume on you will hear it change. If you're lucky it can be eliminated that easily. If not its just down to trying lots of things. Clean all connections. Including grounds, and not just the RCA going in but going out, and AC. Check phono pins. Tear aluminum foil into strips, wrap around the IC. Try another IC. No one knows what it will be so try whatever's easiest first.