I have an Aurender N10 streamer and Weiss 204 DAC. When I connect using the digital coax SPDIF I hear periodic popping sounds in the left channel of the DAC. When I use USB the popping goes away.
It could be a poor contact. Is one (or both) of the s/pdif connections using an RCA socket and plug? They can crackle and pop if a poor match or poor contact, although why only the left I’m not sure, it should affect both channels.