My AMI f120 was modded before I got it. it is mostly original with the old amp still installed but disconnected. an old radio shack stereo amp (very small) was installed and a stereo cartridge installed. I repaired power supply all crumbling cables and have the mech working including coin slot. They installed a white flat ribbon cable (4 conductor) from the tone arm cartridge all the way to the amp. I installed a small stereo amp after removing the radio shack amp. It has a separate output for the base speaker. So its left/right horns and center base. I get a hum that I reduced by adding ground wires to everything. I think I need to get a shielded tone arm cable and wire my cartridge to be Mono from cartridge to amp. what do you think. I select a song and it plays great and loud without the preamp I bought. (cheap) but hum still there. it plays with me as I touch that thin ribbon cable. a fifteen foot shielded mono cable is 35 bucks and I just don't want to throw money away on this. All I need is about seven feet. Thanks. Albert.