10 meters
( 30 feet ) might be too long for unbalanced wires/cables.
humble suggestion:
1) if you have separate preamp with balanced output and power amp(s) with balanced input, you may want to use balanced wires/cable. place the preamp near your turntable and other music playback source. as bro Simon said, shorter interconnect cables.
the amp may be good near the speakers.
2) if you have an integrated amp/avr, maybe place it near your turntable and other music playback source, then use longer heavier gauge speaker wires. again, in this arrangement, shorter interconnect cables.
btw, try to connect your phono ground wire to chassis of your phono amp or integrated amp/avr and see if humming will be significantly be lessen, if not eliminated.
here is a sample phono amp with ground connector (right lower part, below the psu jack)
i am not an expert so let's wait for our gurus to chime in for better info.