Audio Research VT100 MK1 and LS15 HELP!!!


I recently bought this set VT100MK1 and preamp LS15 and while I was at this seller house he demonstrated the sound from his online Tidal on TV connect optical to the DAC Luxman DA - 06 then this go to the preamp LS15 and out into the VT100. This set up sounds amazing at his house. However, when I came home play CD from the Sony X1100ES Blu-ray player RCA output into the LS15 and out to the VT100 and it sound horrible - no bass at all in any type of music.  The sound sometime muffle and not clear and most importantly the bass missing tremendously. Im using a pair of KEF R900 Speakers. What is wrong here? can anyone help me correct the sounds? it is because I didn’t have the Luxman DA - 06 DAC? or it is because I don’t have those fancy hundred - thousands of dollars cable?  or the CD source is playin at 41khz /16 bit not high enough signal?  

This is my first system and I don’t know why I can’t get that high fidelity sound from the ARC equipments.  I'm waiting for the Audioengine B1 to arrive so I can stream Spotify into the LS15.   What is wrong with my set up?  Thank you in advance for helping me solve this.
kentrent
Hey,

So, some thoughts.

If you have some standard electrical wire - i.e. the kind that runs inside the wall - you can use a piece of the ground wire, cut it down and make a jumper wire for the XLR if using SE input. If you have any music on your phone, use a 3.5mm to RCA adaptor and run it directly into the amp. At least you can isolate where the problem actually lies. 
Did you check to see if the shorting pins on the XLR inputs are inserted?
This was already suggested by another poster: did you check this?
All your components should be performing well together.  The DAC is not the reason for your problem.  
Are you 100% sure ALL of your components are connected correctly? 
How confident are you knowledge of how audio connections are made?
I've ARC for decades, with now having current pieces, and have always had exceptional performance. 

You were clear, everything sounded good at the sellers house.  Both channels (I presume) loosing all their bass AT THE SAME TIME is unlikely if it was tubes.  CHECK your connections.
Did you make sure your Sony is set to correctly mix down to stereo in it's menu and not set for surround with bass sent to a sub.