answer:You’re picking up some combo of 60 Hz AC hum and RFI (radio frequency interference) making its way into the amplifier electronics. Try some of the following: (1) reduce the cable length. Shorter cables are less prone to interference. (2) re-route the cable. Especially eliminate any runs parallel to other cables—better to have them cross at right angles. Sometimes just re-orienting one section can make a difference. The cable is acting as an antenna—may be sensitive to position and orientation. (3) Make sure the cable is shielded (coaxial, not just a pair of parallel wires) and grounded. The shield should make a metal-to-metal connection in back of your equipment. (4) They make snap-on ferrite chokes that are like little iron donuts that go around the cable. These can sometimes reduce RFI. (5) If you can actually hear talking then it’s either a radio station or something like a CB or walkie-talkie in the vicinity. If you can determine WHO is broadcasting—and if they are a local source, not some distant station—then they might be in violation of FCC rules & you can nail them (by making the government shut them down) once you identify them. In theory you could fashion your own filters from resistors, capacitors, and inductors but in practice it wouldn’t be easy and most likely would worsen rather than improve the situation. Diodes are probably not going to work either, & might make things much worse. Hope any of this helps.