Headset volume low with optical compared to USB

Hello,

I recently got a Steelserie H Wireless, and I plugged the transmitter to my PC using optical for output and USB for input (which can also be used for output). I have a Realtek HD audio card, onboard with the motherboard.

When in windows audio settings I select USB output in the playback devices, the sound has a good volume range (up to "painful for the ears") but it feels close to the ears, rather flat, whereas when I select optical output, the sound gets really volumetric (like it's filling the whole room), so great quality, but the maximum volume is barely good enough, really low (and both PC volume and transmitter volume are at max). Is that normal ? And is there something to do to improve the volume level with optical ?

Thank you

Well just a follow-up if someone is interested : I didn't solve my problem. I wrote to Steelserie and after asking me to do a few basic manipulations, they asked me to fill a warranty return request, which I did. They then accepted it, only to recant it 7 days later with no explanations. Luckily I hadn't sent back my headset yeta at that time. So I guess I just wanted to say somewhere that Steelserie has shitty support...

Else if someone has an idea I'm all ears.