Headphones

I don't think they exist. HDMI extractors exist, even ones with earc, but there aren't any HDMI to analog cables. HDMI cables use a digital-only signal, and they need a decoder and a DAC to work. I don't think there's anything that can fit into a cable. And USB 2.0 already has all the bandwidth that a multichannel audio signal could ever need. Uncompressed 32bit/384khz x 2ch comes out to 24.576 mbps. You would need 20 channels of that to max out a USB 2.0 cable (480mbps max). 32/384 is already rare as fuck, and 20 or more channels of audio only exist in studios and professional environments. This is headphones, so all you need is 2 channels. On top of that, studios generally work with 24/96 at max, so that comes out to 4.6 mbps for 2ch.

I really suggest you do some more reading. 48gbps is meant for video, not audio.