Pdjmwj I always set bias by ear, starting at the manufacturers recommended setting. In your case, that would be the pre-set amount. Often, I find that the recommended amount is too much, and in many cases end up with no bias compensation at all.
But I set VTF the same way, starting at the recommended setting and then listening for the best sound quality.
But I set VTF the same way, starting at the recommended setting and then listening for the best sound quality.

