I found that the XDuoo you recommended does have a toslink, runs on battery and is powerful enough for my needs. I could sell the FiiO and get the XD-05 basic from aliexpress and it’ll probably solve my issues I guess. And as a bonus I could probably run it on a Anker Powerbank that I have to get more juice out of it.
But I’ll call an electrician anyway, I have some expensive electronics and my PC is my workstation, I can’t play the russian roulette on that. I guess I was lucky that “only” the headphones died.
By the way, thanks for the suggestions! I’m glad I created this topic here, it’s been really helpful
I got the headphone back from Sennheiser, they replaced the right driver, the coil was busted, just like the first headphone.
I sold my FiiO K5 Pro and got a Xduoo XD-05 Basic. And I’m loving it, it much better built than the FiiO, it reeks quality on the materials and buttons. Supplies plenty of power for the HD660s. I’m running it with a Anker power bank and optical cable, I’ll have to keep recharging it until I move to some house that has grounding.
What I noticed from the XD-05 Basic is that it doesn’t make any popping noises when I turn it on or Off, I guess it mutes the output when turning off.
I also made a different cable for the HD660s. I bought a new cable from sennheiser and Soldered a Mini XLR on the middle of it, so it’s acting like a Y Splitter. It’s pretty convenient actually, I can change the cables without fear of damaging the headphone connections and disconnect the headphone without shorting the 6.35mm jack.