Updated: Dec 26, 2019
The SLS-HPULN power supply consists of "two rails in series", each can deliver up to 2.5 ampere from 5x LT3045 (parallel) regulators, resulting in an Ultrahigh PSRR of 76dB@1MHz for EACH rail. This is pretty good, so good that it doesn't make sense to power it with another regulator, an audio grade transformer is definitely a good decision to deliver power here. Nevertheless some customers have other concepts of recification or buffering power, in this case a rectifier / diode would waste power resulting in unnecessary heat. In this case one is good to decide for "DC" as an input option.