Well it is a day. Why not do it now.
Want moeg.
Short version.
Headphone path: PC -> USB cable -> cheapo USB-to-optical converter -> optical cable -> FiiO D03K DAC* -> RCA cable -> CTH + SDAC (but bypassing the SDAC part) -> TRRS extender -> V-Moda BoomPro -> SHP9600.
*powered by an old USB charger plugged into the wall, not powered by a PC USB port.
Mic path: BoomPro's mic -> TRRS extender -> TRS extender -> pink mic jack in motherboard.
I used to have a mobo with optical out so I could skip the cheapo USB-to-optical converter.
And another solution that worked was to use the Apple USB-C to 3.5mm adapter DAC connected to a USB C port on the PC, and then connect a male TRRS to 2 x female mic-and-headphone splitter to that, and then on the headphone side a 3.5mm to RCA adapter to go into the CTH (again skipping the SDAC part) and on the mic side the mic directly into the splitter via a TRS extender.
Connecting the SDAC or the D03K to the PC via USB reintroduces the ground loop.
So in short, you can either:
- Use optical somewhere in the chain to break the ground loop
- Use a single device to perform both the DAC for the headphones and the ADC for the mic - in the above example, the Apple USB-C to 3.5mm adapter, which does the job quite well.
Thank you for coming to my TED talk.
EDIT: obviously if you aren't using a headset with a single cable for mic + headphones, then this won't be an issue, and you won't need to jump through the hoops.