"Bought a cheapy video capture cable "

May be the issue.
Record a chunk and see if sound is there 'after' recording.
It may be a situation where monitoring audio is not possible during the process.
I can't recall if my desktop device allows sound during the process.
There is a lot going on as audio and video get interleaved during the process.


I do not work here, but the benefits are still awesome
Make your sound your own!