Bah Hum Bug

I don't know your equipment, but hum can be a real downer.

You might try a different set of phono cables. Some cables have the shield connected to the ground plug at both ends, which can create a ground loop. Other cables have no shielding at all (a la Kimber Kable), and others ground the shield only at one end, usually marked with an arrow. That end should be plugged into the phono stage, not the table.
Try some different cables (cheap ones might be fine for testing this) or make your own.

The fact that you have hum on phono and not CD is probably due to the extra gain through the phono section. There might also be hum on the CD inlet, but at a level too low for you to hear.

If cheater plugs (lifting the ground) didn't help, I doubt you have a ground loop through the AC line. But it helps if all your gear is plugged into the same AC line. Even a small difference in potential (a few millivolts) can show up as a hum.

There are also some "humbuster" types of products which are basically tiny unity-gain transformers that you can insert in your cables to galvanically isolate two pieces of gear. The good ones are not cheap, but might be worth trying (borrowing if possible).

Hopefully one of these ideas will get it!

Is it the same with other cartridges too?

so annoying. the fact that your system is dead quiet with the CD input seems to eliminate the pre and the power as a source of the hum. so it's the TT or the phono - which are both way more sensitive than any other piece of gear. i had a TT pickup mobile phone data signals over the system if my iPhone was to close to it.

getting rid of hum is a process of elimination. so i'd double check the gain/load setting on the phono. and if you've got other equipment nearby that's not associated with music playback i'd turn all of that off to see if that resolves the problem then start plugging in one by one to double check. cable boxes are prime offenders.

2nd to Jmc.

I have had similar problems and it was the cable that connected the arm to the phono preamp. However, I can easily get noise if I raise the gain too much. I mean more gain than it would need to be very loud. So, I agree with those who suggest cable problems. I use a very low output moving coil, and perhaps a "louder" cartridge would be worth a try. I use Kimber Silver Streak between my Denon 100th anniversary cartridge and Parasound JC-3. Pre amp is Audio Research LS 17. I need very little gain for high volume, and I am frankly surprised by how quiet it is. Good luck, you may need to find a helpful shop.