USB/volume weirdness

I’ve got this weird issue where the volume on my pc changes by 30 or so decibels when I plug in or unplug a USB device. It’s usually my phone, but it’s happened with a memory card reader and a couple of other items. The sound runs through the SPDIF out to my stereo receiver, and it doesn’t matter which USB port I use. Back, front, even the wall powered USB hub I have. I recently upgraded my board, cpu and ram, and it still does it. My os is Windows 7 64 bit. Any ideas?

Does it always change to the same amount? I’m imagining a setting somewhere that sets the volume to a certain level based on if the machine thinks a usb sound device is plugged in (kind of like how you can set the monitor brightness on a laptop based on if it’s plugged into power or not). I have no idea where this setting would be, sound devices in control panel?

That’s a weird one, for sure.

Yes, it seems to be bout the same. I’m basing it off the amount I have to adjust my stereo volume when it happens (the readout tells you db). I’m also wondering if it’s a setting somewhere, I’m hoping someone can just point it out like it’s super obvious:)