Hello Gerard, I run Traktor 2.10 with 2 Kontrol X1 Mk1 Controlers, 4 channels (no timecode) on a DJM 850S.
I always set the gains on the mixer itself (0db), and I disabled the autogain and limiter functions on Traktor - this is very important.
- Disable autogain / limiter on traktor;
- Double-click the 'main' output knob on traktor interface to return it to 0db (always keep it at 0db);
- set the eq type to classic (z-iso will alter the audio)
- disable the eq section on traktor interface to not touch it accidentaly.
- set your gains on the mixer itself always as close as possible to 0db;
Always use a High quality USB Cable ( I run Chroma L-conector USB's).
Audio quality on my setup is excellent - no problems at all.
Sorry for the poor english, i'm from Brazil
Good luck!