SMA style connectors as shown were designed to handle RF signals up to 18GHz, and were never intended to be used at audio frequencies.
They can of course be used for audio: occupying almost the same space as an RCA connector; have the advantage of being locked (that is, the outer connector is threaded and the connection is made by screwing the plug onto the socket), but the centre conductor is fragile and SMA connectors are not intended for repeated mating and demating.
I know of only one audio equipment manufacturer who used to use these connectors, and has now replaced them with RCAs.