Is a preamp needed ???

What amps you’re using....tube or SS. Depending on rest of your system, you may be alright with Lumin T2.  

What other digital sources you’re referring to? T2 will only allow you hear music stored on a external HDD. It does not have any analog inputs you typically found on a preamp. 

In any case, I would bring in the T2 in your system and let your ears guide you. 

Technically speaking there is nothing preventing you from connecting the T2 directly to a power amp.  The T2 has a volume control. 

The question is if the preamp stage that is built into the Lumin is better or worse than an external preamp?  I will preface this by saying that I have not tested a Lumin preamp stage and it will depend on the quality of the preamp you are comparing it too. 

I have tested the preamp stage in a PS Audio Directstream DAC vs. three separate preamps paired with three different power amps.  I could not find a scenario where the preamp in my DAC even came close to a standalone preamp.  In all combinations the soundstage was flatter, less dynamic and noisier than a separate preamp.  It's not that the DAC Preamp stage was bad, just not as good.  

In fairness, the preamps I was comparing to were the Ayre K5xeMP, PS Audio BHK and an Art Audio Conductor so all spectacular units.  

That exercise made me realize how important the preamp is in your system and I view it as a non-compromise component now.  

b_hol
could I use the lumin t2 connected directly to my power amp for streaming without sacrificing audio quality?

Of course you can, your Lumin T2 has 6v available from it's xlr output and 3v from it's rca output enough to over drive any power amp, and it has a Precision 32-bit internal digital volume control, why aren’t you going direct, as this will give you the most transparent dynamic sound.
Any active preamp will colour the sound with it own distortions and to a lesser degree any passive preamp will also.

Cheers George

The question is if the preamp stage that is built into the Lumin is better or worse than an external preamp?

Doesn’t matter, as the Lumin’s "preamp" (output stage) is still in the signal path, there is no bypassing it.
Why run one preamp into another, series’ing up all the distortions, the last one doesn’t get rid of the first ones, they just accumulate.


Cheers George

@b_hol

Yes I think the volume control on the Lumin is very good. Some prefer it over a separate pre-amp. Just need to be careful using the app volume control.

You should:
- Use XLR if your poweramp supports it
- In Lumin app, set digital audio output to OFF
- Enable Volume Control
- Use a really low volume before starting playback
- Listen for any abnormal things such as hum (due to ground loop or other connection issue)
- Be prepared to stop immediately if anything abnormal occurs
- Raise the volume slowly only after you think the setup is working normally