Disk drive selecting a global digital-to-analog setting for a plurality of heads

1. A method of selecting a global digital-to-analog setting for a plurality of heads in a disk drive, the disk drive comprising a plurality of disk surfaces and a plurality of respective heads, the method comprising:

adjusting a first digital-to-analog setting for a first head to generate a first signal;

adjusting a second digital-to-analog setting for a second head to generate a second signal;

selecting a first scalar setting for scaling the first signal;

selecting a second scalar setting for scaling the second signal; and

after selecting the first scalar setting and the second scalar setting, selecting the global digital-to-analog setting in response to the adjusted first digital-to-analog setting, the adjusted second digital-to-analog setting, the first scalar setting, and the second scalar setting.

2. A disk drive comprising:

a plurality of disk surfaces;

a plurality of heads actuated over the respective disk surfaces; and

control circuitry operable to select a global digital-to-analog setting for the plurality of heads by:

adjusting a first digital-to-analog setting for a first head to generate a first signal;

adjusting a second digital-to-analog setting for a second head to generate a second signal;

selecting a first scalar setting for scaling the first signal;

selecting a second scalar setting for scaling the second signal; and

after selecting the first scalar setting and the second scalar setting, selecting the global digital-to-analog setting in response to the adjusted first digital-to-analog setting, the adjusted second digital-to-analog setting, the first scalar setting, and the second scalar setting.

3. The disk drive of claim 2 , wherein the global digital-to-analog setting comprises a write current setting.