Do I need a dac

Not really! The DAC in the Lumin is high quality! Using an external DAC is likely to be a sideways move! 

Great thank you would a roon improve it 

Roon will not improve your wallet. Some report that it comparatively hurts the sound quality. I didn’t notice that, but it is not for me.  I have never read that it improves ANY SQ.

An external DAC could be worse or better depending on your taste, the resolving power of your system and spending ability.  Most likely diminishing returns  make it too expensive for most.

These guys above are absolutely correct

Only if the DAC you buy is better than your built in DAC. I'm streaming from a Node 2i and was using my Parasound's DAC. I bought a used Aqua La Voce S2. It made a tremendous difference.

An Audio Research Reference DAC would be a significant upgrade. Audio Research DACs are incredible and very complimentary to other Audio Research components. I could not believe it when I paired my ARC Ref 5SE with a ARC DAC! Speaking of synergistic… detailed, natural, dynamic. 

If you are still searching for a "better sound," you should attempt to understand what you need from your system that is missing. You may spend a lot of $$$ on a "better" DAC, but still not get the result you are listening for. It is impossible to make any further comment, you have to drive forward your pursuit of the sound you want.  

Excuse me but what you've done is put a quality revealing component in front of your Lumin, so it's doing it's job and revealing all the faults of your Lumin.

Upgrading your DAC won't change the quality of sound you're getting from the Lumin, it maybe even make it worse.

Maybe some streaming gizmos may help but eventually you'll need to upgrade the Lumin if you want better sound.

the t2 has a fabulous dac built in 

if you want a differentsound then change the sound by getting a different dac

or try a different dac/streamer

or try to tune the t2

you can try the lumins dsd conversion tab in options

if you need setup or tunning advice on a lumin please contact our store

Dave and Troy

Audio intellect NJ

lumin dealers

If external DACs quality and specs will be at least like your T2 internal DAC or better, SQ will improve.

Hello, 

The T2 is really great and great for the money as long as you use the internal DAC. 
The only thing I would suggest is a linear power supply. If you are out of warranty you can use a $400 SBooster. If in warranty you would void the warranty if using a LPS from a third party like SBooster. It makes a big difference. If you are willing to try a different preamp then Lumin just released the P1. It is an all in one preamp, DAC, and streamer with a LPS already built in. Plus, they say the sound beats ghe T2 and almost as good as the Lumin X1. I am in line to do an at hone demo. This store in the Chicagoland area is a Lumin/ SBOOSTER dealer. You can even demo the LPS for the T2 in your home. 
holmaudio.com

I think you would be good either way. I hope this helped. 

If I had your preamp, which I think is awesome, I’d get a better DAC.  Not that the DAC in the Lumin is bad at all and I’m sure it’s not, but I think you can do better depending on your tastes. 

I bought a aesthetix pandors eclipse dac and wow what a difference