I recently moved and connected my new Cox Contour DVR to an audio receiver and TV. (A Blu-ray player is also connected to the receiver and TV; this may or may not have any relevance to my issues.) There was a pretty bad hum so I inserted an isolation transformer between the cable feed and the DVR, which eliminated the hum. I measured the voltage between the outside of the cable connector and safety ground with a cheap VOM and found 0.2VAC and 1-9 mVDC. I have a number of questions that I hope someone can answer for me.

Is this voltage difference the cause of the hum?

Was my measurement approach appropriate?

Do the measured voltages indicate that the cable is improperly grounded?

If the cable were to be bonded to the house neutral with 3/0AWG, would this likely eliminate the need for the isolation transformer?

Whether it would eliminate the hum or not, should I have it done?

Does the cable company have any obligation to do it in order to comply with regulations?

Bob Simon
New Orleans