Rythmik F12 and Sierra-1 Issue's

[sludgeogre]

Do i need a Y splitter for the red/white input of the sub or can i just do 1 cable from either red or white to say Sub 1 on the NAD?

I'm also curious as to why its not working the original way I had it setup, when it has worked in the past for extended periods of time.

I used to use a Y splitter from a preamp to my sub and integrated amp and it worked great, but since you want to use the subwoofer crossover, you just need a preamp after the DAC, then into the sub and then the amp. The sub just doesn't like a full line level signal as others have said. If it worked in the past that way maybe you were using volume management from something else? If you were, you'd have to change the volume on the sub any time you change volume on the amp, because the sub wouldn't be controlled by the amp's volume knob. Anyway, buy a Schiit SYS for 50 bucks and you'll be good.