DVD players have inherent ability of decoding MP3 but play standard CD as it is - without compression. They offer pretty good tracking but got bad rap for sound because their analog output stage was often pretty bad.
Digital cables can add substantial amount of jitter (translates to noise in frequency domain) by reflections (on characteristic impedance boundaries) or by system noise that affects edge transition. High quality transport can often be a curse when they have coax output slew rate in order of few nanoseconds instead of typical 25ns found in common CDPs. Such fast transitions require very careful cable impedance matching. On the other hand fast transition is less susceptible to system noise providing better timing (lower jitter). Optical cable, often much worse when system has noise affecting either transport or DAC but can be a blessing in the system that has ground loops.
Digital cables can add substantial amount of jitter (translates to noise in frequency domain) by reflections (on characteristic impedance boundaries) or by system noise that affects edge transition. High quality transport can often be a curse when they have coax output slew rate in order of few nanoseconds instead of typical 25ns found in common CDPs. Such fast transitions require very careful cable impedance matching. On the other hand fast transition is less susceptible to system noise providing better timing (lower jitter). Optical cable, often much worse when system has noise affecting either transport or DAC but can be a blessing in the system that has ground loops.