Works fine with Audio-gd DAC-19 (10th Anniv. model - 2015) and Schiit Audio Bifrost 4490 DAC.
http://www.audio-gd.com/Pro/dac/DAC1911/DAC19EN.htm
http://schiit.com/products/bifrost
Tested systems:
RPi3 w/Digi+ & RuneAudio --> Audio-gd DAC-19 --> Cavalli Liquid Carbon --> Hifiman HE-400i
RPi3 w/Digi+ & RuneAudio --> Schiit Bifrost 4490 --> Schiit Vahlalla (ver. 1) --> Sennheiser HD600
Tested SPDIF Coax and Toslink of Hifiberry Digi+.
Used 16/44.1 and 24/96 FLAC files from USB hard drive (Toshiba Canvio Connect II) powered from RPi3 USB port.
