Aftermarket system - random noise issues.

[rocknstang]

I have the 401A package but decided to upgrade the whole system.
Focal 6 1/2 2-way components up front.
Disconnected the center channel and 3 1/2 mids in the upper doors.
Left the factory rears.
Upgraded to 8" Rockford Fosgate sub in the Shaker sub box.
Alpine X-A90V 5 channel amp.
Bypass factory amps using Hextalls550's harness.

The Focals sound fantastic! But I get 2 different noise issues randomly.

This morning I made 2 different round trips to church.
Leg 1: Had a static noise like loud Rice Krispies in the left front speaker. No altenator whine.
Leg 2: No crackling, but bad altenator whine. For about 10 minutes, then there was a little pop and the whine stopped!
Leg 3: No noise whatsoever! Sounded fantastic.
Leg 4: Altenator whine all the way home.

So I can't predict what my listening experience is going to be. It could be noiseless, or either crackling or whine that may or may not just stop mid trip.

A local shop did the install. Any clues where we might start diagnosing? Many thanks!

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[UserName]

Kinda hard to determine what it is from behind a screen but here are a few questions that may lead to a solution.

What kind of wires did you use?
What gauge wire for the amp power?
Where is the amp located?
Did they run the power and RCA wires close to each other or down separate sides of the car?
Have you checked all power connections to ensure proper securing?
Where did they get the positive power from?
Have you done the "big three"?

 

[rocknstang]

Did more tests today. Don't have time for details but I ended up removing the turn on lead wire from the amp. And it still came on! Checked the voltage and they had tied into the 6v audio enable signal from the head unit.

Talked to the shop and we both agree that the amp is bad so they are replacing it Wednesday. More later.

 

[rocknstang]

Update.

One thing I failed to mention in the OP was that the amp would turn on even if I just opened the trunk. Then after a few seconds it would shut down then power up again. This same behavior if I just opened the door.

Took it back to the shop today. After some diagnosis they determined that the amp was fine. It apparently has turn on capability from the RCA lines.

So why was popping the trunk or opening the door causing the amp to turn on? The typical gremlin - grounding problems. What solved it for me was noise suppressors (?) on the RCAs. I guess the RCA grounds we're floating or something causing all kinds of noise problems and strange amp behavior.

 

[West TX GT]

Is it not the door chime that is triggering the amp turn on since it then detects an audio signal? I am pulling signal from the rear speakers and using the auto turn on feature to power on. In my case I am certain it is the door chime that causes signal which results in power on. I don't see it as a problem as it turns off after a little while with no signal.

 

[rocknstang]

Is it not the door chime that is triggering the amp turn on since it then detects an audio signal?

I don't hear a chime when I open the trunk only but the amp turned on. But that was only part of the problem. The other part was the random noise issues that seemed to come and go.

Regardless, the issue appears to be resolved. I believe they just used either a PAC SNI1 or something similar. Crystal clear sound, no noise.

This amp takes either high or low level signal through the RCA connectors. And there is a switch to tell it to expect either high or low. Alpine didn't explicitly say this, but I would think the RCA turn on feature is only supposed to work when in High input mode (speaker level). But because of the ground loop issues with the RCAs and the extreme noise, maybe the amp interpreted that as high signal even though the switch was set on Low.

Adding the ground loop isolators solved the remove turn on problem being triggered by the RCAs.

They did run a wire to the fuse box to get the 12v turn on. Not sure which fuse they attached to but the amp comes on when I crank the car and it goes off when I open the door. No pops, crackles or whine. I'm happy now.

 

[UserName]

Rock on. Glad you got resolution. I find it very strange the amp would turn on upon trunk opening though.

 

[rocknstang]

Now that I've had the system a while I'm finding some areas for improvement.

1) I'm not convinced the amp is truly putting out 300 watts into my 4 ohm 8" RF sub. I've got the gain up to about 75%.

If I play a song like AC/DC - Who Made Who at about 3/4 volume, I notice that the sub kicks OK but it barely blurs the side mirror. This sub is rated for only 150w RMS. I would think it would be very taxed at these volume levels.

So I found a 50 Hz test tone mp3. Loaded onto a USB drive and played it. At about 60% volume the sub is so taxed it feels like it's about to jump out of the box. So I'm reasonably sure now that the sub channel can output the rated wattage. But...

Q1. Why would an mp3 test tone play with more volume out of the head unit than pretty much any other mp3 song?



2). The Focal 165FX sound crystal clear but I've noticed the baritone range is rather weak. To test this I downloaded a test tone app, plugged my phone directly into the front RCA inputs and played the range of test tones up to about 2K.

What I noticed was the range from about 200-500 was rather weak and above 500 was very strong. I assume the test tone generator puts out each tone at a constant amplitude but it may not. The test tone test is consistent with my ear test.

So now I'm considering adding a TwK88.

Q2. Would you agree that a TwK88 would help or is there something else I should/could do before going that route?

BTW - on the head unit I have the bass up about 2-3 notches and the mid and treble down 1 notch.

And as far as I know nothing has been done to the doors for sealing or sound deadening. Just replace the door wooferd with the Focal woofers.

Thanks!

 

[2016Gruv]

Q1. Why would an mp3 test tone play with more volume out of the head unit than pretty much any other mp3 song?

The short answer is because music is dynamic and not a steady tone. It also depends how hot the source material is. I would never judge low frequency ability using music in mp3 format.

 

[rocknstang]

Ah. Ok. Thanks!

 

[scott_0]

did you do anything to alter the factory processing that is present?

 

[rocknstang]

did you do anything to alter the factory processing that is present?

Yes, I had made this change about a month ago...

ACM 727-01-02 x0xx xx

it was

ACM 727-01-02 0300 34

I will double check later today.

 

[rocknstang]

Another question.

I notice that my voltage gauge wanders between 12 and 14 vilts even when I'm playing at a low volume. It'll sit at 12, 12.5 or 13 for a minute or two then jump to 14 for a little while then back down to 12 - 13 for a minute or two then back to 14.

If I unplug the amp completely, it stays rock solid at 14.

Is this normal?

 

[rocknstang]

Another question.

I notice that my voltage gauge wanders between 12 and 14 volts even when I'm playing at a low volume. It'll sit at 12, 12.5 or 13 for a minute or two then jump to 14 for a little while then back down to 12 - 13 for a minute or two then back to 14.

If I unplug the amp completely, it stays rock solid at 14.

Is this normal?

Bump.

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