buzz from one phono preamp more than another?

My Lehmann black cube se makes way more buzz, enough to be annoying, than my Grado ph-1. The Grado buzzez as well , but just barely. I've been back and forth w/ three prong adaptors, different circuits of my house etc. and have run out of ideas. Except a power conditioner. Would that help? I hate spending a lot of $ on something for no results. I'd just swap them out, but the Lehmann sounds better on my stereo. No hating, I even have a brand new Grado Reference Sonata 1 cartridge($5-600 new) that sounds absolutely killer. Except for the hum on the Lehmann. Any ideas would be much appreciated