Sounds like perhaps the transformer in the DBX is giving off some RF or 60 hz hum. It might just be in the wrong location when paired to your Eden where it's RF is susceptible to being picked up. You could try to mound the DBX under the Eden.
If your a DIY tech you could try to relocate the DBX's transformer within the chassis or even try adding an RF shield around it... just thinking out loud here...
Edit - oh, I just remembered there's a trick to reducing hum in the WT400 where the tech would loosen the toriodial transformer and rotate it 30 degrees then retighten. It could be the fields of both transformers are adding and creating a hum large enough for the tube to pick up??? Not really sure.
Last edited by MuthaFunk : 12-15-2013 at 12:10 PM.