user14578: 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.  

user41425: 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

14578: <p>Many older amplifiers support wired remote control through connector jacks or ports. My 10-year old Marantz also supports this function, using <a href="http://manuals.marantz.com/NA8005/NA/EN/DNTXSYlyopmtcn.php" rel="nofollow noreferrer">a simple RCA connector</a>. </p>

<p>Originally these were used with <a href="https://www.wehkamp.nl/Winkelen/KenmerkAdviseurArtikel.aspx?CC=C26&amp;SC=6F1&amp;KAC=F17&amp;artikelNummer=582788&amp;MaatCode=0000&amp;BC=GOA&amp;BAC=ALG&amp;cm_mmc_o=7BBTkwCjC-kTwFwwECVyBpAgfkblfbETzplCjC-ggwllBbywCaeCCjCoxDonIoo&amp;utm_source=google&amp;utm_medium=cpc&amp;scid=scplp865827880000&amp;sc_intid=865827880000&amp;cm_mmca1=12913-AGI-23705142542-ASI-168204110942-865827880000&amp;gclid=CM_xnPTb3dICFUkQ0wodeoAHGg&amp;gclsrc=aw.ds&amp;dclid=COrKpfTb3dICFdGWdwodqCgDSA" rel="nofollow noreferrer">external IR receivers</a> when the unit was not kept in plain sight.</p>

<p>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.  </p>
 41425: <p>According to this thread on <a href="http://www.remotecentral.com/cgi-bin/mboard/rc-theater/thread.cgi?4877" rel="nofollow noreferrer">remotecentral</a> 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 ;)<BR>
The RC5 codes and their functions are in this  <a href="http://m.us.marantz.com/DocumentMaster/US/Marantz%202014%20IR%20Command%20Sheet.xls" rel="nofollow noreferrer">nice excel sheet</a> or use <a href="http://www.remotecentral.com/cgi-bin/codes/marantz/" rel="nofollow noreferrer">this information</a> if you want to send raw hex</p>
