The keyword here is "basic USB", or poorly implemented USB audio. Yes, it's mediocre.
But well implemented asynchronous USB audio, and especially the new UAC2.0 interfaces such as Lorien's WaveIO, Amanero's Combo384, and exaDevices exaU2I, are claimed to be the best-available digital front ends (currently) for computer based audio.
And don't assume S/PDIF is ideal! S/PDIF TX adds jitter, and S/PDIF RX adds jitter.
Sure, a S/PDIF TX stage might "iron out" the jitter from a poor USB receiver, but it would be more sensible to use a better USB receiver in the first place!
The only good reason to use a USB-S/PDIF interface is for people who have an existing investment in a good quality DAC with S/PDIF input ...
... which leads us to murillollirum's V-DAC MKII. This is a modestly priced DAC, and it's not clear (to me) how good its USB receiver might be.
Would a separate USB-S/PDIF interface feeding the V-DAC be better than the V-DAC's own USB input??
murillollirum, you might need to experiment, yourself.
Mmm, there are cheaper options -
for $60 there's a well-regarded (XMOS based) USB-S/PDIF interface here -
XMOS 384kHz high-quality USB to I2S PCB with ultralow noise 6.5uV regulator | eBay
for $55 the miniDSP miniSTREAMER is TE7022 based -
miniSTREAMER | miniDSP
or for $40 CM6631-based -
CM6631 24bit 192kHz USB to Coaxial and Fiber WLX | eBay
But you're spending money to improve the front end of a DAC that is not exactly high end. This money might be better put towards a good DAC/USB receiver combination -
$145 will get you the well-regarded Objective DAC (ODAC) with ES9023 DAC chip, plus the respectable TE7022 USB receiver -
Objective DAC (ODAC) - RCA Version
The same component choices, though not quite of the same construction quality, are available from HiFimeDIY for a ridiculous $60 -
HiFimeDIY Sabre USB DAC 2. External PSU, 96khz/24bit - ES9023+TE7022 + Coaxial OUT