And if you have the 3.5mm to toslink cable for the chromecast puck you could use iit to test the optical in of your amp.
How so? I just went to check and I don't see how it would work. there's no 3.5mm jack and that connector doesn't have a way to insert into the optical port.
Getting up to the stereo to mess with this stuff is sketch level 8, very fun.