The SX10 is not designed as an "integrator" endpoint, so is not officially supported with other input sources, but, yes, it is the same connector and pinout as on the SX20 and could be used with an external audio mixer, although, as mentioned, this is not a Cisco supported configuration.
Wayne
--
Please remember to rate responses and to mark your question as answered if appropriate.
Wayne
Please remember to mark helpful responses and to set your question as answered if appropriate.