Allen & Heath Xone 42 with Traktor?
Hi, my question is: can i use xone 42 with traktor without a soundcard?
No. You will need an audio interface that can output between two and four stereo channels. Also, you will need some sort of transport control, be it deck-style controllers like the Behringer CMD PL-1 (http://www.behringer.com/EN/Products/CMD-PL-1.aspx) or something less traditional such as the Kontrol X1 (http://www.native-instruments.com/en/products/traktor/dj-controllers/traktor-kontrol-x1/)
Question
And what about xone 23c. Will I be able to use two channels in traktor?
nope… what you need is something like an Audio 2 from native instruments or a 2i4 focusrite, 2x4 presonus… wire the outs to the ins on the mixer
Well, you CAN use the sound interface of the xone:42 for traktor.
I aggregated the xone interface with my onboard sound card to one virtual sound device. The master signal goes out of the xone:42 and the monitor signal out of the headphone jack of my notebook.
BUT you can´t use the normal faders and eqs. The sound card of the xone:42 uses the mic-channel, so you only have the high/low knobs and the “fader” is the level knob.
Due to the lack of midi in the xone:42, I used a midi controller to eq, fade, etc internally in traktor. So the xone:42 was used (can only be used) as sound device.
Yes, you can use the Xone 23C without the need for an additional sound card - assuming you don’t use timecode.
Hardware Question, Hardware forum. 
What? The 42 doesn’t have an audio interface…
The 42 has a 1-up 1-down interface.
Huh. Well, that’s new… And pointless.
Not pointless!!
I use it for recording, sounds way better then the mic in on my laptop