Some basic recording tips for anyone having problems with RF interference, hiss, niose, hum, groundloop etc.:
1) Make shure all your recording gear is grounded properly and gets its power from the same power supply source in the house (put all audio equipment in the same wall plug).
2) Always use shielded cables for audio signals and try to go digital.
3) Use balanced audio connections (XLR, TRS).
4) Try to seperate audio cables from power cables. Dont just put them next to each other.
5) Use the shortest cables suitable for the distances in your recording space.
6) Wall warts: Plug them in all facing in the same direction and bring them away as far as possible from the other audio equipment (especially guitar pickups).
7) Lighting in the room: get rid of dimmers if possible.
8 ) Computers: Turn your guitar in different directions while sitting / standing at your recording spot to determine the best (quietest) direction to place your computer. I've got the best results by putting the PC on my left side facing me with its small front and forming a direct line with the guitar on my lap while sitting at my recording desk).
9) Cell phones: Put them away as far as possible from audio gear and guitar pickups or turn them off.
10) Turn off anything with an electrical motor (eg. girlfriend's hair dryer, kitchen mixer, vacuum cleaner, air fans, airconditioners, ...).
11) Use humbuckers and get rid of your old CRT monitors
To find other sources of interference, just put your guitar's pickups near to various things to detect RF emissions.
Cheers, Max