I'll go along with that also Al,
1: The dac's power supply for the output stage as PM states is not up to it.
2: If the dac output buffer is not low output impedance <300ohms, as some very weak tube output dac are today some I've seen up to 3000ohms.
3: The impedance load as seen by the dac output is so severe that only something like a Krell preamp's output stage at 1ohm output impedance is able to drive it.
Cheers George