So you can save your wav and feed your cpc with a cassette adaptor.
Then if u add some lines on the real thing and you need to save?
I really don't know if this adaptor will send it back to your pc's line in

.
On my 464 I have modded the pcb so there are in/out ports.
You must find the right recording volume at your line in and record it with audacity or audition.
Then load your wav to ape.