Properly earthed (at one end) STP would probably be OK, still not an ideal situation though, over short runs its fine, in my D-line trunking running up to my TV I have
o Power (to a 6 socket extension)
o Ethernet (to a switch)
o Speaker Cables for rear surround speakers from Pioneer Amp
o Subwoofer Cable
o Sky+ HD Twinax cable
and everything works fine
