things to know about your cassette deck
is it able to use chrome cassettes or does it only use normal bias tapes?
DAT line out to cassette line in. right?
Make sure you are not saturating the cassette. type I peaks at +1, type II peaks at +3. No more. And preferable not much less for peaks.
No compression should be NEEDED for a decent tape.
Your cassette machine manual list its tech specs at what? S/N ratio? and frequency response?
When recording on my deck, if a put the tape selector for one kind of tape and put a different kind of tape in the macnine to record on, the resultant recording is really bad. Muffled and quiet.