Need Help w/ a Rogue Audio 66 LSR Magnum

I'm slowly upgrading my system and finally retired an Adcom preamp that I had for many years.  Picked up a Rogue 66 Magnum that was factory refurbished recently.  It sounds great but adding it has created a hum in the speakers that isn't present with the Adcom.  All of my cables have also been recently replaced.  I don't know how many hours are on the tubes, which are Electro-Harmonix.  The Rogue is the first tube component I have owned.  My amps are two Murano P200S monoblocks and my speakers are Acoustic Research Classic 18.  Even with the volume at zero, there is some hissing coming out of the speakers.  I don't think I have a speaker issue since they were serviced a few months ago.  The person I bought it from didn't have any humming when he used it.  I've already disconnected everything except the preamp, amps, and speakers to try to narrow down the culprit.  The RCA outputs are switchable between active and passive.  Both outputs are currently in the active position.  What else should I do to get the hum and hiss to stop?