Years ago i replaced the cassette player in our 1999 diesel truck. The ongoing problem is an intermittent popping of the stereo at startup. There is a loud 'pop' and the unit shuts down. The aftermarket system includes a CD player, 2 channel amp and pair of 6x9 speakers in the front door.
Over the years, I've swapped a few used CD players, swapped a few new amplifiers and cables. Even changed the brand of speakers at least twice

I ran new speaker wires to the doors
The amp goes straight to battery (with fuse) and is grounded to the floor close to the amp.
The stereo unit's negative wire is run to the outside firewall.
Solder all wire connections and heat shrink wrapped them

It doesn't pop each time, but when it does it always on start up. I've done lots of aftermarket systems and never had this issue.

 

What happens when you turn the key to accessory, Does it still do it or is it only when starting the engine?

 

Great question and i'm not sure of the answer so i'll do some research and report back. thanks!