Do you think I need to use the direct mode with A-100 for HD 700s?
I don't know. I don't think you'll damage things either way unless you accidentally turn the volume too high like LCseminole says. Try both?
Transport: Sony UBP-X700 UHD-Blu ray player spdif PC using Musiland Digital Times WASAPI via BNC connection - DAC: DC-1->XLR XPA-1 , RCA->Basx A-100 CD: Denon DCD 600 PCM 61 DAC. RCA Amp: XPA-1 gen 2 using XLR connections. Speakers: Axiom Audio m80 V3, Sennheisser HD700 headphones. two pairs 12 guage each bi-wire speaker cables per monoblock Headphone amp: Basx A-100 (INCREDIBLE VALUE!!)