I have been playing with optical glass between my server and my MUTEC MC3+/REF10 reclocker. I haven't tried any in the higher dollar range. Do different designs and constructions matter? Are the SP/DIF AES/EBU digital cables better?
I have my primary audio pathway, and I have a lesser audio input from my TV. I use the Nvidia Shield Pro with USB out with the signal downsampled from surround to full range stereo. The downsampling to full range stereo option is starting to be lost on new products and definitely some apps; they do not pass the the subwoofer channel or the LFE (low frequency extension channel). The result is stereo output cutting off at about 80hz (also probably not the best downmixing algorithms)! I guess they've decided anyone using stereo has a very limited cheap system. For me any dollar spent on surround is money I could be spending on glorious STEREO
So I am ditching my USB path (USB out of Shield > Kitsune Tuned Singxer SU02 USB to i2S converter > Holo May Dac) and am using a HDMI Audio extractor (which will downsample up to Dolby Atmos surround into full range stereo and even allow some bass control etc.) with toslink out to my May dac. I have started with a cheap extractor, have a pro one on order, and cheap found toslink cable. Already I like the sound better than the USB/i2S output, it never sounded right, kind of wooly and muddy. I think that is more about the software/drivers of the Shield than about the interface.
I will be getting a few toslink cables to try here. In the past, I have heard differences between cheap ones and purpose built ones. It will be interesting what a difference will show up with the May, as it has heavy engineering chops to reduce the type of jitter that has been endemic in toslink interfaces.
I am getting a Supra Zac Toslink which is supposed to be good. But in audiophile circles the Lifatec cable is usually recommended as the best sounding one. Also the Wireworld SuperNova 7 is mentioned a lot. I'll post here as I try stuff. Did you find anything?
Eons ago when I had an Audio Synthesis Transcend / Dax Discrete combo, they used a bespoke dual ST glass interface. Besides generic and industrial cables, Aural Symphonics were the only audiophile option. I couldn’t get comfortable with the cost but did try their io-gel contact enhancer and found it to be effective.