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
Ive demoed certain components to find that dynamics, bass, warmth, etc. were lacking incredibly. Could you ask the seller if they can come over and possibly bring the dac with them? Could you demo different components at a local shop? any professionals that can look at at your setup? 
@akiravelvet

the speakers he has is 

Pure audio project - Quintet 15



ive tested the r900 speakers with another amp and its sounds wonderful much bass and strong. Switched to the ARC i just bought its missing about 60% bass compared to the original amp i have (MAC1500). And tonight I discovered the LS15 one of the tube (V3) has white sparks when i turn on. So now i can only conclude that either the preamp LS15 or VT100 amp is defects. I contacted the seller and he’s not responding- avoiding me. So I’m kinda bumped and feel down that this happened to me. I wanna ask him for money back but i doubt he’ll give back.
Did you receive owners manuals with your purchase?  If not, you can find them on-line.  They should help explain the XLR jumpers.  They are little "U" shaped pieces of metal that the seller should have provided.  Make sure you place them in the way ARC indicates.  
@alphaguy65
The Op is using balanced cables from preamp to amp. Maybe he should try RCA unbalanced.

I've also listened to the R900's with only 30W; very large cabinets with deep bass, huge soundstage.

@kentrent  Something we haven't discussed is your speaker setup and your room.

((And tonight I discovered the LS15 one of the tube (V3) has white sparks when i turn on.)))Some tubes flash upon turn on which is normal. Make sure you're on the 4-ohm taps and your speaker wires are in phaseand speakers not too far out into the room.