Thank you for contacting Samsung.
You will need to refer to your Marantz product manual or contact their support group for questions regarding that device, specifically related to its operation, features or the best way to connect it to 3rd-party devices, since we are not familiar with another manufacturer's unit.
And since ARC is not working when the STB is connected directly to the TV, you would need to make sure that if ARC is enabled if is included as a feature on the receiver. In order to use ARC with Samsung products, AnyNet+ must be enabled. To access the AnyNet+ feature, you would need to click MENU on your TV remote and navigate to System > AnyNet+ (HDMI-CEC).
If you have any additional questions, we suggest your refer to your product manual or the product support page on our website, where you'll find a comprehensive troubleshooting guide, product support videos, FAQs and How-Tos, as well as manual, software, firmware & environment downloads.
Thank you for being a Samsung customer!
The Samsung Online Support Team
answered 1 year, 10 months ago
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