Turntable Hum

Hi. My set up is a Rega Planar 1, Pro-Ject Phono Box MM pre-amp, and an Era 300.

The minute I turn the Rega on a massive hum is present. I have scoured the internet and tried everything I can find.

Tried grounding the amp and the left channel output on the Rega. Tried grounding to each other, and each one to a radiator. 

Have tried all combinations of plugs being in the same expansion lead or not.

I have laid it all out so no cables are crossing. 

But no improvement.

If I plug the Rega straight into the Era 300, there is no hum (thought the sound is nor great, but just about listenable).

I also get the buzz when I use a Bose speaker I had to hand to test.

Any ideas?

TIA.