Rob,
If you are serious, and the 505 is decent enough, take it to a good tech with a Maxell UDXL II or IIS cassette and have it internally tweeked for that formula. The noise floor will drop substantially, everything about the recording will be better. Maxell makes a very durable, dynamic and clean running product with a stable housing. Sony also makes a great tape, although it tends to be expensive and not discounted much. Good luck.
If you are serious, and the 505 is decent enough, take it to a good tech with a Maxell UDXL II or IIS cassette and have it internally tweeked for that formula. The noise floor will drop substantially, everything about the recording will be better. Maxell makes a very durable, dynamic and clean running product with a stable housing. Sony also makes a great tape, although it tends to be expensive and not discounted much. Good luck.