JAZZ BASS " HUM " VERSUS A " BUZZ "

[Makatak]

I see a heap of threads about the " 60 cycle hum " on J Basses . Im a bit confused as my 2 J Basses [ Before I did the hell sheilding job ] had a buzz that went away when I touched the bridge or strings ....... particularly annoying when recording/practicing in a room with a dimmer switch on the lights or a bad earth loop in the building wiring .
My question . Is the buzzing the 60 cycle hum , or just a bad sheilding problem ?? , because now that my basses are sheilded , they are as quiet as a mouse even under dimmer lights , but according to folklore you cant get rid of the 60 cycle hum . Whats the buzz ?

[mech]

The buzzz is an electrostatic field (radio) in nature and the hummm is an electromagnetic field that changes polarity.

Common items that generate electrostatic fields are fluorescent lights, anything with a microprocessor, light dimmers, some amplifiers or effects, etc. The human body is a good antenna for radio frequencies or electrostatic interference and your proximity to the pickups and other electronics will inject the interference into them. When you touch a grounded part of the guitar you're grounded through the cable, amp and wall socket and the noise you pick up is shunted to earth ground. Metal blocks electrostatic fields and fully shielding the electronics in the bass usually cures the problem of your body being close to the signal paths. If the building wiring does not have a good earth ground, shielding the electronics in an instrument may not help.

Electromagnetic interference is generated by power transformers as the magnetic field alternates polarity. This is the 60/120 Hz (USA) and 50/100 Hz (220-240 volt countries) hum. This is a changing magnetic field sensed by the coils in the pickups. Single coil PUs are very susceptible and Humbuckers were developed to cancel electromagnetic interference.

J basses normally have PUs that are out of phase electrically and magnetically. When used as a pair, rather than individually, they are in phase when sensing the vibration of the string. Since the out of phase magnets are not part of the coils sensing electromagnetic interference and the coils are out of phase, the hummmmm is "bucked".

mech

[Bass from Hell]

one thing that can help is this, to get a cleaner current thru your amp, hum-xhttp://www.ebtechaudio.com/humxdes.html