this is a quote from the usrecordingmedia website. This section is on how to choose a test tape:
maybe a re-bias isn't necessary?
I just ordered a some 1/2" 456 and GP9 and some 1/4" 456, GP9, and 406 for mixdown (they still don't have 1/2" 406) to do some "experiments".
If anyone's interested I can post a clip of the first song I recorded on my E-16 which was on GP9 (biased for 456) and another song on 456 to hear the differences. of course you can't conclude much from one song but I am going to do a whole bunch of songs and switch the tape a couple times just to see which is best for my needs.
Re-bias as well as checking tape tension IS REQUIRED if you want your heads to survive 2006 with GP9 or the hoards of other high-output tape formulations.