i was wondering why i get this 'ripple' effect when doing a loopback with my Duet 2. (balanced out > in, using Mogami 2534 XLR > 1/4" TRS cables)

(44.1 kHz sample rate, 512 buffer size)
also, i was wondering if it was typical to have low level 'noise' from this type of cable/loopback. this is the loopback connection with no signal passing through...it has a 'harmonic' or tone. (it does not always show up @ the same frequency) is this 'OK' or do i have a problem (interference?) and/or need different cables?
and when i unplug the cable, the 'tone' goes away and i have nice clean noise floor...so clean you could eat off it...

(...this is a screenshot of 'realtime' analysis, so level values are +/-...)
*side note: and why is Signal Scope saying Duet2 has 2 ins and 4 outs...looking at the Duet2 it seems it is the exact opposite of that...