W210 CDI - ellimate "pop" sound when starting car

[datripsta]

I'm fitting a Google Nexus 7 2013 with USB DAC feeding sound processor via optical. The processor feeds the amps ( just like an analog X Over). All in place of command 2.0, All factory fitted stuff has been bypassed with new speakers. All works well except a load pop when I start the car. I've yet to mount the nexus in the dash which is the next job once I sort out the popping sound.

I'm using the live feed from the cig lighter as this goes on / off with ignition - this 12v ignition live feeds a relay which is then feeding all units with remote on off and a further daisy chained relay to same cig lighter feed which gives 12v switched power ( eg the USB port which the nexus is connected to for power with OTG cable - the nexus is set up to turn on and off when it sees or loses power on the USB ) - because I have a custom Kernal loaded on the Nexus that goes into deep sleep I don't need 12v permanent live as Nexus uses battery ( will last 2-3 weeks in this sate ) to be fair right now I'm using a USB cig lighter charger rather than the hard wired USB just because its easier until I mount the Nexus in the dash.

The issue is when starting then car the voltage cuts for a spit second which is causing the pop sound down the speakers. The sound processor has a short delay built in but its not long enough for the glow plugs to warm up in the morning so I get the pop hen I start and its bloody loud !

Does an "always on" 12v ignition live feed exist on a W210 CDI. A feed that's not cut when the car starts but goes off with ignition. As I've got the relays set up I just need something that will trigger the relay to go on when ignition is on but not cut when the car starts.

Failing this would some kind of capacitor work - something to hold enough charge to prevent the blip in power. If this will work anyone know what I would need ?

The fun will begin when I link up to the steering wheel controls ......

TIA

 

[bob6600]

I think the capacitor may work. I have an amplifier and mine 'pops' everytime I start the car. It's annoying and at first I thought it was the obvious bad earth but it wasn't. Wires are all of good quality and as the battery is under the rear seat, the RCA's are not run anywhere near the power cable. I was going to fit a switch on the remote lead to power the amp but never got round to it.

Check the earths but I don't think you are doing anything wrong. Funnily enough I have thought about doing the exact same install in my W210 and would be interested in seeing your set up so pics are a must!

 

[datripsta]

yeah same here, I don't believe its wiring. All good quality, correct size cables well earthed and every connection soldered into plug ends. I spent a long time making it good and nice to prevent any issues. I don't use RCA but my initial run was with RCA and had no buzzing etc.... just the annoying pop when starting the car.

I just need to find out what capacitor to use. I've no clue about this other than the principles of capacitors. I just need something that last about 1-2 seconds. I think if I put the cap on the feed from cig lighter all issues go away as the switch live feed is from relays which the cig lighter 12v triggers on/off.

Once done I'll sort out some pics.

 

[datripsta]

I just found this :

Accessory Pop

Accessory pop is associated with one particular electrical event in the vehicle. This can be switching on your turn signal, headlights, brakes, windshield wipers or even the rear window defrost. These high current drawing accessories are causing a voltage spike that is traveling into your car audio equipment with the result being heard as a sharp pop. Adding a small bi-polar capacitor (0.47 uF) between the accessory's power wire and ground will often absorb these surges. You may need to place the capacitor on the load or the power side of the switch (maybe both). See the diagram below to see how this is done. Note that the diagram is slightly different if the accessory has a relay in the circuit.

Full link > Car Audio Noise Troubleshooting

 

[datripsta]

this seems to be a better solution

Speaker Pop & Capacitor