Is it possible to hear the difference or how the AD-2 PRO quality is affected ?

For measurement purpose, the ADI-2 pro (FS) is a clear winner, while you are able to configure the DAC output asymmetric or symmetric to the front jacks and using TWO DAC's.

This means, better SNR & best channel separation as it get's. The ADI-2 DAC comes with one DAC...

Hp

With very good equipment (speakers, amps, room treatment etc.) you can easily hear the improvements of the PRO FS over the PRO (blind tests with several customers).

If you can save a substantial amount of money, go for a PRO, otherwise always an ADI-2 PRO FS.

+1

I also bought mine from Sweetwater. I have tried both the the FS and the non-FS (a friend's unit) simultaneously using two laptops manually sync'd and switching between two inputs on my preamp, and honestly I could not tell the difference in an ABX test.
I did do a full set of bench tests and the FS does measure a bit better due to what looks like a reduction to close in phase noise, but even knowing that we could not hear it. My system is pretty resolving- a benchmark AHB2 amp and electrostatic loudspeakers/subwoofer or Sennheiser HD800s/ STAX SR-L700 with energizer, and we used 96/24kHz music files from a variety of sources. The listening room has acoustic treatments and has been set up using the XTX room analyzer II PRO, and I prefer the sound of the loudspeakers to the headphones, and it's not even close...
Nevertheless, I am glad that I purchased the FS and Sweetwater has been excellent both in this purchase and prior ones, and their after sales support is exemplary.

*Sweetwater.  What an Outstanding Purchase Experience on my end also!

HOW they were able to virtually ROCKET my RME to me during the Christmas Holiday is beyond me.    Post Sale Follow-Up was most Noteworthy!!

Curt

*Ghost Rider:  It is probably best for RME to address your Question directly.   Perhaps MC (RME) will pop in...

Existing Units are already Clocking Internally at 1Ghz.    What could lay beyond that Extreme Accuracy is beyond my abilities.   

Trust me...You WANT the ADI-2 Pro! 

I'm sure that RME will correct me if I'm wrong, but as a relatively recently retired designer of "femtosecond" clocks for communications/fibre optic links that were in the c. 100fs region I suspect that what they mean is actually sub ps not sub fs.
The SINAD of the RME units don't seem to have appreciably changed with the release of the fs version (again, please correct me if I'm wrong) and arguably, from an audio perspective, that's all the matters, and maybe not even that so much with SINADs greater than 110dB. Nevertheless, their goal of constant improvement in their products is extremely laudible.

Hi All,

Thanks to all comments. Just to avoid confusion I got my ADI 2 PRO FS version.
Connected it to my Laptop. Connected my Focal Elear headphones.
Played for around 20 minutes.
Now the unit is very hot. Bottom side is too hot to touch even.
Is it normal?