I bought one of the Quadras recently for an older semi-retiree who needed a web cruiser and for $29 it’s a good deal, but according to Inovato support, the port labeled “AV” on the Quadra is S/PDIF, and not supported currently. Sound is delivered via Bluetooth (with an optional dongle) or HDMI.
But the older guy likes his youtube vids and he doesn't have a Bluetooth speaker.
IF your HDMI monitor has built in speakers you should be fine. However, my monitor does not and Bluetooth speakers run some money. My salvation was a $22 gizmo on Amazon. The description from the seller was “Avedio links 4K@60HzHDMI 2.0b Audio Extractor Splitter Converter, HDMI to HDMI + Optical To slink SPDIF + 3.5mm Stereo Analog Audio, HDMI Audio Embedder Inserter for PS5, Xbox, Optical Fiber Included."
The unit included the converter box, a short HDMI cable, a short fiber optic cable & USB phone brick and cord.
Installation is simple and the ports are marked in & out. Power to the little USB-C input. Speakers to the 3.5mm jack, HDMI from the Quadra to HDMI IN and HDMI OUT to your monitor. Easy peasy. I tested the unit on some youtube music videos and they sounded great through some $8 earbuds.
The unit is just begging to be attached to the Quadra with some Hook & Loop material for a neat organized look.
Sound problem solved without being too pricey.