What is the fine-grained topic of the following text: The X7 Mark-II utilizes an 8-channel ESS ES9028PRO DAC coupled with three crystal oscillators and topped with an included amplifier module sporting custom-designed op-amps; all of this means a significant improvement in jitter-reduction, soundstage preservation, and other aspects of conversion over its predecessor, the X7—a unit that was nothing to sneeze at in the first place. Only return the topic.
The improvement of the X7 Mark-II's audio quality over its predecessor.