Audio Research LS-25 and REF 2 preamps have a Processor selection that allows the use of processor input. The big advantage to this selection is this is a straight feed thru, where you can use the volume controls on your processing device. This is also possible with other preamps using one of the inputs. The issue is: if you want perfect volume alignment every time you need to break out the dB meter. I use a surround receiver RCA outputs going to the "processor" input on my ARC LS-25, connected as usual to my 2 channel high end gear. I use no center, since the cost of a center to match my 2 channel speakers would far exceed what I want to spend on HT gear.
