Need help with DIN to RCA phono cable troubleshooting

Somehow, I am currently having an issue with an apparent ground problem with my DIN (female five pin straight connector) to RCA phono cable. The arm is a Dynavector 501 mounted on a custom plinth, supporting a Garrard 401 table.

There is a reduction in overall volume, bass frequencies are MIA, and this is all accompanied by a loud hum. I have tried doing a continuity test from a spare headshell to the ground cable, and RCA terminations. I can't tell where the ground was interrupted, I need guidance in how to test for proper continuity in relation to signal and ground leads. Also, I don't know where the shielding should be connected, so a thorough explanation will be needed.

 Thanks for any help that can be given.
 Regards,
 Dan