I was just curious how consistent the sound of the antihum pickups was during the 1960s? Do the earliest ones sound about the same as the ones Guild was installing on guitars in 1970? Have people who own say, a 1964 Guild Electric with antihums found that it sounds very similiar to the same model with antihums from 1969? I ask because I know first-hand that the early '70s HB-1s sound distinctly different from mid and late '70s HB-1s. It seems other companies have this evolving pickup sound phenomenon too, the most famous example being Gibson's PAFs in the 1958-1962 period sounding different (arguably superior) to Gibson patent number pickups in the mid to late 1960s.