Hi:
Tascams often have a small switch in the back to turn the noise reduction on or off; be sure noise reduction ("dbx") is ON.
Tascam also has real good support forums (at least they used to, I haven't checked in a while). I would try tascam.com & go to support/analog forums.
Good Luck! Some of the tape based Tascams can produce real nice recordings.
Regards,
C