Audio too loud from Blackmagic breakout cables

I've got our Blackmagic card (on PC) audio out plugged directly into our monitor speakers. When editing in Resolve, the speakers are too loud to comfortably listen to. Our neighbors would complain! This is with the PC speaker volume set to the lowest setting (1).

Ideally, I should probably have a mixer in between the BM card and the speakers. But am I missing a virtual mixer setting somewhere in the software?

I also have a loud hiss when I play any audio from other programs (Premiere, Windows Media Player). That suggests there's a volume setting set too high somewhere.

On the cards I have featuring the breakout cable, I can lower the audio output levels in Desktop Video for both AES and analog.

That's what I was hoping. Drilled into the Decklink Studio audio settings and backed off the Analog Audio to -12. We'll see if that helps.