What fuse does a car amplifier use?
A car amplifier needs an in-line fuse within 18″ of the battery on its dedicated power cable. Smaller amps (under ~500 W RMS) use MAXI blade fuses; larger amps use ANL bolt-down fuses.
Why a separate fuse is required
The amplifier's power cable runs directly from the battery, bypassing the vehicle's fuse box. This cable has no protection unless you install an in-line fuseholder close to the battery. If the cable chafes against metal and shorts, an unfused cable can start a fire. The fuse protects the cable, not the amplifier.
Fuse sizing
The fuse should be rated at approximately 125% of the amp's maximum DC current draw. Calculate the DC draw:
DC current (A) = RMS watts ÷ (12 V × amplifier efficiency)
Most car amplifiers are 50–70% efficient. Use 60% as a conservative estimate:
| Amp RMS output | Approx DC draw | Recommended fuse | Fuse type |
|---|---|---|---|
| 150 W | 21 A | 25–30 A | MAXI blade |
| 300 W | 42 A | 50 A | MAXI blade |
| 500 W | 69 A | 80 A | MAXI blade |
| 750 W | 104 A | 125 A | ANL |
| 1000 W | 139 A | 175 A | ANL |
| 2000 W | 278 A | 300–350 A | ANL |
Many amplifiers also have a built-in output fuse rail — these protect the amplifier's internal circuits and are separate from the main power cable fuse.
Built-in amp fuses
Most amplifiers have a row of glass tube fuses (AGC, fast-blow) on the top or rear panel. These are internal protection fuses and are specified in the amplifier's service manual. Replace only with exact amperage and type.