Hi there. 
A bit of a longshot but here it goes. 
I am trying to use the Beam as a stand alone speaker without the 70ms delay. The intended setup is as follows:

My sound source is a DJ Mixer which has standard RCA output (left/right, white/red cable, you get it) 

I want to convert this into HDMI ARC in order for the Beam to accept and play.

Question, what gadget will i need inbetween to convert the signal??  Some says that a TV inbetween can do the trick but surely there has to be another solution with a smaller size gadget. Like a preamp or something?  Would a laptop/mac work as inbetween gadget?
 

FYI i have no intention to stream the sound into other Sonos devices, ONLY the Beam. 
Thanks in advance