OP: likely you have a damaged internal amp chip or speaker proper as you toslink digital signal cannot be modified from it's S/P delivery protocol.
I have a small one just for convenience in front of the TV with a small self powered "sub" on the floor.
But The Simulated surround or stereo mix down from the optical (S/P dif ) is pretty bad. Lots of resonances, delayed internal reflections and resultant "vowel" colorations on voices along with odd voluem imbalances from senter dialogue hard panned sound effects. I used to be an audiophile but I don't have amuch hearing above 7Khz anymore. But I can still hear problems from mid bass through upper vocal and first overtone range. All soundbar solutions under 400 bucks sound like garbage to me.
MY issue is my analog out on the Xfinity box is not good so i will have to take the audio off the HDMI. The previous box had a good stereo mixdown with ow distortion.
I suppose I should get a small HT receiver that will allow a stereo mix down. I'm not in the mood to have speakers all over the place.
Though Yamahaha amps are just "meh" sounding, they used to do digtal processing well.
Anybody know if any of the smaller, inexpensive HT receiver have a decent mixdown capability where i can strip digital audio off the HDMI ARC input ?
I'm done with toslink. I can appreciate the galvanic isolation, but the optical amps and receivers appear to be poorly implemented in most modest HDTV and cable boxes.
I was thinking of buying a pair of the excellent for the money previous model Wharfedale Diamond 10.1 bookshelf speakers. They are super inexpensive right now. Maybe sold out!