Here is my Teach Z6000 although not the same model as the OP's. A wonderful sounding machine, and I find that DBX recordings sound great also. I've heard online stories about the notorious DBX pumping sound, but this one makes a clean sounding recording if DBX is used or not. Built like a tank, and works with a wide variety of media because of its adjustability.
The Z6000 seems to really like recording and playing type IV Metal tapes. I believe I read where they were set up for TDK tapes, but it just did a really good job on a Sony metal select tape.