Radio electrical question

[cfriedman67]

I installed a Soundstream Bluetooth amp and 4 Polk audio speakers. They play when I turn the car on through my iphone. The issue I have is when I turn the car on the speakers will crackle for a second as well as when I turn the car off. Any suggestions on why this is happening. The amp is hooked up directly to the battery, there is also a keyed power wire that is hooked up as well.

Thanks Craig

[Just puttering]

What engine and carb or efi?

By chance, is it crackling while its running, you just cant hear it? Haha

I assume if its keyed power is off, it stays quiet.

Look for 12v radio filters.

[cfriedman67]

1997 cobra 4.6. It is quite with key power off. Only crackles really when car is turned off and only for a second. I will look into it. Thanks.

[Railroad]

Could be an electric motor winding down, ie fan, fuel pump, air duct blowers, heater, a/c, etc.

[narly1]

Wondering if the crackling sound is because the circuitry for the Bluetooth (which is wireless radio frequency) link between your iPhone and the amp is "dying" faster than the audio power amp circuitry (which likely has some large storage capacitors in it) at shutdown.

To prove my theory unpair your phone from the amp first and then turn it off and see if the crackling goes away.

[Papa]

Wondering if the crackling sound is because the circuitry for the Bluetooth (which is wireless radio frequency) link between your iPhone and the amp is "dying" faster than the audio power amp circuitry (which likely has some large storage capacitors in it) at shutdown.

To prove my theory unpair your phone from the amp first and then turn it off and see if the crackling goes away.

I was suspecting this as well. Bluetooth is a frequency hopping radio with a digital frame structure that could be translating the out of sync or partial payload packets as noise over your audio system. There is about 10ms of lag that is typical with Bluetooth, and a 1.28 second resync period where the audio equipment could be getting partial packets or out of sync data. The test that narly1 recommends would be a good way to see if this is what's happening.

[cfriedman67]

OK. I turned off Bluetooth on my phone and still the same. When I shut the car off the speakers crackle for a second. I also listened carefully and there is very low level hum/hiss coming out of the speakers when the car is keyed on. This very low level hum/hiss is there if the Bluetooth is connected or not.

[narly1]

I don't have a lot more for you to try.

The only other idea I have would be to temporarily disconnect the amplifier's power wiring from your car (both battery and keyswitch) and connect them to a separate, independant battery sitting on the floor.

Then go through the iPhone connect -> listen for hum -> disconnect iPhone -> power down amp & listen for crackling sound sequence again.

If the hum is still there it means that there is something going on with the iPhone to amp wireless connection. You could try another phone to see which one it is...

If the power down crackle sound is still there it's an issue with the amp and not related to it being connected to the car.

My instincts tell me that the crackling will still be there and that the amp itself is the source.

[Old Timer]

Most amplifiers have a delay, when the switch turns on it is a bit before the amp comes on.
I wonder if there is a way to delay the power. There is a small delay box you can use on
air conditioning systems, you can get delay on power, or delay on loss of power.
https://www.amazon.com/Supco-TD69-Ti...dp/B002JP6YSQ/
This would delay the power going to a relay (only good for 1 amp)
so you could delay it until after the engine is started.
I don't have an idea on turn off.