A loud pop when the ignition turns is the amplifier switching on while the head unit is still settling, and the resulting transient goes straight into your speakers. It is fixable and it is worth fixing.
What is happening
When power reaches an amplifier before a stable signal does, the amplifier faithfully reproduces the switch-on transient from upstream. The larger the amplifier, the larger the thump, and a subwoofer takes the worst of it.
The usual causes
- Remote turn-on taken from a source that is live before the head unit stabilises
- Head unit powered from an accessory circuit that drops during cranking
- A ground fault that lets the amplifier see a voltage swing at switch-on
- An amplifier without a turn-on delay circuit, which is common at lower prices
Fixes, in order
First, take the remote turn-on from the head unit’s dedicated remote output rather than from an accessory feed. That output is designed to come up after the head unit has settled.
Second, check the amplifier ground against our grounding guide. A marginal ground causes turn-on thump as readily as it causes whine.
Third, if the pop persists, a turn-on delay module holds the amplifier off for a second or two after the remote signal arrives. They cost very little and they solve the problem outright.
Popping on shutdown
The same logic in reverse: the amplifier is still powered when the signal disappears. The same delay module usually handles both, and correcting the remote source often fixes shutdown popping on its own.
