If the input impedance of the amp is less than 30K, ARC preamps will tend to be bass-shy. There was a thread about this just a few months ago.
Pass XA Monoblock Amps with Audio Research Preamps
Have any of you Pass XA.5 owners matched up your amps with the Audio Research LS-27, Reference 3, or Reference 5 preamps. I own the Pass XA100.5 Monos and appreciate your thoughts related to this combination of a solid state amp with tubed preamp. Thanks Stephen