Bad Cartridge?

My system is dead quiet until I set the cartridge on vinyl... then it hums. Any ideas?

HW-19 w/ SAMA
Sumiko Premier MMT Tonearm
Grado Ref. Platinum Cartridge
Cary SLI-80
Sonus Faber
Sony SCD-1 'for background music' 8-)
Is it grounded properly?
Damn... its the SAMA! To get it in the right position, it is touching the wood base. I'll cut out part of the corner frame on the base so it won't touch... see if that does it.
It was the SAMA... it was tight against the corner brace of the wood base. Fixed!