I recently purchased a Wharfedale SW-150 for my little room. I usually connect a sub to my CA540A via a SINGLE phono-phono lead, using the pre-out LEFT (white, mono) input on my amp. Just now however, I connected it to my amp using a standard phono cable, ie to the left AND right input of on the pre-out. When I connected to L and R, the subwoofer seemed to be louder/more powerful, which I like. Am I doing anything wrong using standard phono instead of the usual mono-single-phono sub cable plugged into the L channel of the amp (ie the mono channel)?