i kept having issues with data tapes made on this specific recorder, and it turns out it has like zero isolation; if you plug in the input and output cables at the same time you get hella noise. doesn't help that both cables are going to the same computer, so you've got ground wire feedback. at least i think thats what happened; it works if I only plug one at a time.
I attached this tingus called a "ground loop noise isolator" and that worked too. Weird! Anyone know how these work?
Edit: Marty from SoundCertified says it works by putting two transformers next to each other, converting the electrical signal to magnetic and then back to electrical again, allowing it to "bridge" two circuits without them sharing a common ground wire. Neat!