As topic, i was wondering. Because i am planning to buy an external sound card (maybe a Focusrite) but is a mixer is good as well? For example a DJM-900NXS

Can. DJM-900NXS have built-in sound card. Just download the driver from Pioneer website. And you need to install ASIO4ALL also I think. Haven't played for quite some time.

In terms of technical or sound quality, does it works better than a pure external sound card? Or it is just a same as a built-in sound card from PC?

Hmm.. I don't think that there's any noticeable differences between using an external or built-in sound card.

Just wanna add that I used 2x CDJ-2000NXS + DJM900NXS last time. All connected to Traktor using built-in sound card. So I'm not sure about the software that you mentioned.

You literally using a sound card from the mixer right? Can someone correct me lol. Basically if you select the DJM as your i/o (there's setting in the Traktor whereby you could select which sound cards as your preference), the Traktor will use sound card from DJM as output.

I think there's differences between using an external sound card or built-in sound card. I do music production, therefore would like to know this

Yes literally using built-in sound card from the mixer.

Not sure about the quality differences. My soundman last time is very fussy about sound quality. But never complaints anything about using built-in sound card. So yeah, if by logic, using dedicated sound card should be better. But gonna be really troublesome when you have gigs anywhere and need to bring all the stuffs.

The only sound quality differences that we care is the music file itself. Either .wav, or .mp3 (320kbps above) only.

I'm not gonna bringing my stuff everywhere, that's why i am considering this kind of set up.

Before .wav or .mp3 creation, quality in production from DAW has to be good as well ( which is where i am concerned ).

Thanks for the response though!