low level hum

So the other day I noticed on the lead out track a low hum.I can also hear it on the lead in. It is not noticeable when music is playing and disappears as soon as the tonearm is lifted.I am using a Pro Ject 2 xperience with a dynavector 17d3 cartridge into a PS Audio GCPH. What is going on I never noticed this before. I've had this combo for about 6 months now.
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So it seems the hum is coming form the speed box. Hum disappears when it is set to 45r.p.m. and when it is totally disconnected.Has any one else had a problem with the
speedbox II. Is this a defective unit or is this a common problem?Will the speedbox SE or the music hall cruise control 2 have the same problem?
I have the identical problem with my Speed Box 2 / mmf 2.2 TT. I have a call into Music-Direct - we'll see what they say. The hum is gone with the original music hall power supply. I am using a Shure V15VXMR cart.