Here are the
IR signals for the DV-7600 (and all other Marantz DVD players). Use AV Separates and select DV-7600 from the drop down list.
The Sound Mode button sends RC-6 System code 4, funtion number 80. It is described as "Switch the Play mode SACD 2ch > Multi > CD > (Toggle)".
If you have a remote that can accept Pronto Hex:
0000 0073 0000 0013 0060 0020 0010 0020 0010 0010 0010 0010 0010 0020 0020 0010 0010 0010 0010 0010 0010 0010 0010 0010 0020 0020 0010 0010 0010 0010 0020 0020 0020 0020 0010 0010 0010 0010 0010 0010 0010 0BCD
Or if you have a cable remote made by UEI like Comcast or Atlas, use setup code 20539 or Video 0539,
manually program EFC 00144, and teach the signal to your Marantz remote.
All RC-6 IR signals employ a toggle bit in the IR signal, which must flip between 0 and 1 on each successive transmission of a signal. The UEI remotes know how to do that, but a learned signal doesn't flip the bit since it was learned in one of the two toggle states. Since you'll probably want to press the Sound Mode button more than once to cycle through the possibilities, you'll need to press some other button which sends RC-6 system code 4 after each press of the Sound Mode button. One way to get around this is to set up a macro that sends some other signal in addition to the Sound Mode signal. I'd use EFC 00040 which I believe the DVD player won't respond to, or this Pronto Hex:
System 4, function 077
0000 0073 0000 0012 0060 0020 0010 0020 0010 0010 0010 0010 0010 0020 0020 0010 0010 0010 0010 0010 0010 0010 0010 0010 0020 0020 0010 0010 0010 0010 0020 0020 0010 0010 0020 0010 0010 0020 0020 0BDD.