If you’re using a factory radio without a remote wire, you might be wondering how to turn on your amp. In this case, there are a couple of things you can do. The first thing to check is if you are already using some type of high-low adapter.
Assuming you are running a sub BAM with your factory OEM head unit, you can buy a high-low adapter with a trigger built into it. This adapter will sense when the stock radio turns on and will give you a remote output that will trigger your amplifier. When you turn your radio off or your ignition, the high-low adapter will kill that trigger. The cool thing about this is that most high-low adapters with the trigger built in have a delayed turn on and a delayed turn off. This helps eliminate any kind of turn on and turn off pops that you might get.
If you purchase a high-low adapter without a trigger built into it, you can run a wire from your ignition switch to your amp. This will turn the amplifier on and off with the key. Alternatively, your radio might have an accessory at the radio which is your red wire typically on an aftermarket. Most factory radios still have some type of switched power there unless it’s controlled through data. In that case, you’re probably not going to find one there, but there are alternative places like a cigarette lighter. If a cigarette lighter turns off and on with the key, you can tie in power there that will turn on your amplifier.
You’ve got to find some type of switched power in the vehicle where you get it. It’s really up to you, and there’s always different locations you can get it at. The easiest thing to do if you’re already installing a high-low adapter is just to buy a high-low adapter with a trigger built into it. That way, you’re already done.