The ornamental design for audio amplifier for automobile, as shown and described.
FIG. 1 is a perspective view of front, right and top of audio amplifier for automobile showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The broken lines showing of audio amplifier for automobile is included for the purpose of illustrating portions of audio amplifier for automobile and forms no part of the claimed design.