Turn-On Thump / Pop
Symptom: Loud thump from subwoofer and/or speakers when system powers on or off.
Root cause: DC offset transient from amplifier as power supply charges. Some amplifiers have poor muting circuits.
Fix sequence:
- Turn-on/turn-off delay relay — Insert a relay between head unit remote output and amplifier remote input. Relay adds 2–5 second delay on turn-on. Head unit powers off immediately, amplifier delayed off.
Products: AudioControl ACR (auto remote delay), generic 12V delay relay, most DSPs have programmable turn-on delay.
Ensure head unit turns off last — On turn-off: head unit should mute before amplifier loses power. If amplifier dies first: uncontrolled DC transient.
Check amplifier mute circuit — Some amps have a "mute" terminal. Connect to a delayed turn-on signal (via capacitor and resistor network: R=10kΩ, C=100μF → ~1s delay).
Replace amplifier — If pop is internal to amp and severe, the muting relay inside may be failed or the design is poor.