Once the manufacture states “4 channel USB Audio (24bit up to 96khz) input & record out” the whole mixer is digital with a DAC on the XLR output just like the typical Digital Mixer. ADC is more than likely after the Phono/Line stage so, the result should not be different than what Pioneer says…
Built-in 24bit/96kHz High Performance USB Sound card – Pioneer developed an onboard USB sound card that can simultaneously handle input and output audio signals from up to four (4) stereo sources through a single USB port1. The sound card supports 24-bit/96kHz high resolution signal processing, and can input and output all audio signals with no degradation of sound quality. Once connected to a PC or Mac, the settings utility tool can be used to customize the mixer's output signal path to suit various purposes, such as DJ play, song recording or production2. Furthermore, smooth transfers between DJs are possible with the easily accessible USB ports on the top surface of the mixer.
Sound Quality Design –The DJM-900nexus is equipped with the same audio input and output circuits as Pioneer's flagship DJM-2000 to achieve the most accurate audio reproduction from connected sources. The 32-bit digital to analog converter supports all outputs of the mixer, including the master audio outputs, booth outputs as well as headphones. Additionally, the built-in high performance 32-bit digital signal processor (DSP) suppresses any digital and analog circuit noise by way of high quality balanced hybrid operation amps and full balanced output circuits.
It appears the whole “Phantom Valve Series” is marketing without any valves in the mixer for, what manufacture have you ever seen do not boast on the type of valve used in their Valve Mixer?