A:

Usually, when this happens, you are setting the preference after it has a chance to take effect. For example, if you set DIG_MIXER_CHANNELS to 128, but do it after you've called AIL_open_digital_driver, then it won't have a chance to apply.

Also remember that preferences are reset by a call to AIL_startup, so don't set your preferences too early or forget to reset them if you ever restart Miles.