Hi!

How broken are the cassette decks you have?

A really cheap and easy solution would be to simply buy a cassette shell
adapter (like the kind use to play portable devices into car radios with
cassette players), put it into the tape well on your deck and then either
play into the deck or record through it. The cassette transport doesn't have
to be able to do any more than raise the play/record head assembly to meet
the head inside the adapter.

You could play a source through the deck, turn on the noise reduction
circuit you wish to use and then listen to the line outputs on the deck. Or,
assuming the HX/dbx circuits are functional in recording mode, play a source
into the deck's inputs, set the recording level on the deck (if needed or
possible) and then plug the shell adapter into the device that will be
receiving the final signal.

I suppose audio quality would suffer in some way by doing this, but the
price is certainly right.

William