Has anyone ever used an external microphone on the Huawei Mate 9 and which cable did you use?

[Gob Shite]

I'm trying to record sound from my old hifi via the phono/rca sockets and into my mate 9 microphone socket (same as headphone socket). So far unsuccessful. Has anyone ever used an external microphone on the Huawei Mate 9 and which cable did you use?