Controlling amplifier using remote control jack Many older amplifiers support wired remote control through connector jacks or ports. My 10-year old Marantz also supports this function, using a simple RCA connector. 

Originally these were used with external IR receivers when the unit was not kept in plain sight.

I wonder if there is a way to control the amplifier using an Arduino, which probably means by generating the required signal over the connector instead of receiving it from an IR receiver. Any pointer to a similar project is appreciated as well.
According to this thread on remotecentral the signal on the RCA connector is just the inverted signal that the IR-LED receives. So if you load an RC5 library and invert the output (0=1 and 1=0), you should be able to send codes to that connector with an arduino. Or even better, use an ESP8266 and control it over wifi ;)
The RC5 codes and their functions are in this  nice excel sheet or use this information if you want to send raw hex