Hi, I just got got a brand new Ashdown ABM 500 EVOIII RC. It produces a slight buzzing (not humming) through the cabs when running, wether some cable is plugged in or not, wether the mute button is pushed or not, even when the master post is completely turned down. I once had an EVO first generation, but I do not remember if there was abuzz with that amp. Might it be because of the fan? Has anyone noticed the same? Shipping the amp back will probably get expensive. So I am trying to avoid the "this is normal with this amp - answer" by the online seller.