Originally Posted by PlanetAVS
Not sure. You might not need one. I don't activate it by voice, I use the cast icon in the Amazon music app. It looks similar to a Chromecast icon if you're familiar with that.
Try installing the Alexa app on your phone and then see if it will pair with your Marantz AVR.
OK, I did that am casting from the Amazon Music app to my Marantz AV7704 processor.
Unfortunately, I can't determine the quality (file type, bitrate, and sampling frequency) of the stream in the Heos app because the "i" button is not available when casting. Using the Amazon Music app within Heos allows you to tap "i" to see the file type, bitrate, and sampling frequency.
Also, within the native Amazon Music app with a couple albums I've tested so far, the stream quality drops a level when casting (for example, HD drops to SD and UHD drops to HD), but you can't actually determine the file type, bitrate, and sampling frequency that is being cast.
So, casting is working, but is apparently limiting the stream quality vs. what is natively available in the Amazon Music app.
Using the Amazon Music app within Heos provides the native HD and UHD streams, but no "My Music", unfortunately.
Net, there does not appear to be an ideal implementation of Amazon Music HD with Heos.