I'm thinking of experimenting with an external DAC to see if it can smooth out the higher treble notes in my Martin Logan 35XT speakers. To my ears they seem a little bright no matter what settings I use. Can anybody tell me exactly how to interconnect a DAC, and is there a way to use the RR2160 volume control with an external DAC connected? The DAC I ordered does not have a volume control. The DAC is a Geshelli Labs JNOG 2.