It's not an Axiom problem since the buzz did not exist with the Denon. It could be a ground loop, it could be a bad connection, it could be a bad amp. I would suggest you work it out with Emotiva. I'm sure they'll take care of you.

LFR1100 Actives,QS10HPx2,QS8x2,EP800,M3x4,M3x2 (Wood),M5HPx2 (Wood),AxiomAir,ADA1500-8,ADA1500-7