Well, Anahata, the 'I' would have been in italics if I knew how to get them into Mudcat posts.
These 'USB soundcards' seem to be intended for gamers to be surrounded by sound ('speakers to the right of them, speakers to the left of them, volleyed and thundered...') and my good speakers are in the lounge, as herself ordained. I just want to get the music onto CD so that I can play it on a good stereo, and also to save it to HD. I've never done any type of studio work, and never likely to!
Not that the little Nicole computer speakers are bad! Better to my ears than some modern skinny column speakers.

From your description of 'looping,' my fears may have some grounds, in that the signal would not be converted from optical to electrical that the computer can use. At present.

I may have been too soon off the mark blaming the new computer for needing a stronger signal, as the turntable, which HAS a preamp, also seems to be the same. Either something is turned off or the onboard soundcard is faulty. Must delve.
Yours and Russ' original suggestions for internal soundcards may be the best way to go, but, new, they cost half the price of a Zoom H4!