I had to install a passive attenuator between my Rogue RP-5 and NuForce STA200 since my Zu Omen Defs are 101 db efficient. The tube hiss from the Rogue was a bit much for my taste. Now, when I was using my Project PreBox s2 as the pre (when Rogue was repairing my RP-5), quiet as a mouse. I'm using a Schiit SYS as the attenuator and now have super quiet playback. I'm looking to purchase a Benchmark AHB2 which has 3 gain settings to choose from.