For the last few days, it is being noticed that whenever I start playing a record, hum is heard by touching the body of the turntable. It happens only when the cartridge is placed on a record & is moving.Hum or extra bass also heard at the end of a record.At that time it feels that sound is not clear. I have tried many options like change of ground wire, replacing the male/female cables & above all replaced two cartridges like Shure m447 & AT95e. But of no result. Any help?