If you want to use the stock bias and eq setting (that's assuming that someone hasn't changed them from the stock values), I'm not really sure about the 900 (or the new ATR tape which may be better for +9-+10 tape) but I've been using the bias-2, eq-2 settings for 911. You should try all combinations of 2&3 though. To take full advantage of the really high output (headroom) tapes like 900 and the ATR Magnetics, you really need to set the bias for that tape. You can certainly try those tapes and see if you like them without doing that (I plan on trying the ATR soon. Like I said, the chances are very good that the 2-2 setting is biased for whatever the favorite tape of the former owner was (or what was popular at the time like Ampex 456 and that's fine). That's how my deck was set up.