Setting up Home Theater with AppleTv4

Hello - Just when I thought I knew a thing or two, I don't!  If anyone can give me some advice I'd really appreciate it.  I replaced my first generation Apple TV with #4.   Of course it's now apples and oranges, no pun.   Gen one Apple TV had an optical cable that connected to the sound system.  Gen 4 eliminated optical and utilizes USB-c.  I'm connecting to an older Harmon Kardon HVR 140, which uses the very old fashioned white, yellow and red cable connectors, or optical.

 I purchased a cable that has three plugs (red, white yellow) on one end and USB on the other and an adapter to convert USB to USB-c.  It  should all work, and it doesn't. Anyone familiar with Harmon Kardon - I've plugged the Apple TV to Video 2 Audio/Video input.     Any Brainiacs available?   I'm stumped.   

Yeah, today's streaming devices are not designed with the audiophile in mind.  Amazon Fire removed their optical output years ago and Roku doesn't have this either.  Most of these are targeting people who just mount a flat panel TV and call it a day.

You could try to get an "HDMI Audio Extractor" like the Panlong or J-Tech devices (under $40).  I don't know how well these work.  But your best bet is likely just to buy a newer receiver.

Does your tv have optical out? You could connect the Apple TV with HDMI and send the audio out of your TV via optical to your receiver.