Humming/Buzzing from Pro-Ject Speed Box II....

hey everyone... hopefully you can give me some insight as to the cause of my problem.
my system is comprised of a pro-ject Xpression III turntable, pro-ject preamp, pro-ject speedbox and peachtree nova amp. everything sounded lovely and worked great until i added the speedbox and now there is a hum as soon as the aux input is engaged... i.e. the needle doesn't have to be down. it's really annoying. i disconnected and reconnected everything but no dice. i moved the pre and speedbox further away from the amp turntable, no dice. any help/suggestions? thanks a lot.