I have a hd 800s. I was wondering if a cable connected to the 800s terminating in a 3.5mm (TRS) connected to a 3.5mm female jack convert plug to 4 pin male XLR would work when connected to a balanced output on an amplifier (with balanced output)
No, this won’t work. The other way around works.
You can connect a balanced cable to a single ended amplifier output with an adapter. This joins the grounds in the adapter and will functionally work as if you were using a single ended cable (which joins the grounds in the jack). It lets you swap easily between balanced and single ended without swapping the cable. This is what I do myself.
You can’t connect a single ended cable to a balanced amplifier output with an adapter.