I'm sure placement is a concern and/or shielding? I built a DIY Cinemag Blue in separate enclosure, wires twisted, etc. It was very sensitive to placement, would hum when near Eros or pre amp. I picked up a Park's Audio Budgie SUT, CineMag Blues, 1:8 / 1:16. He uses a circuit board design, seems it doesn't care where it is placed, it stays quiet.