Alternator Whine, Turn on Thump, system hiss!

[Ryan33]

Hello everyone,

I am lucky enough to be experiencing these symptoms. First off, alternator whine. I believe the culprit for this is that the 2 amps in my trunk are grounded in 2 different spots, creating a ground loop. I was told this is the issue 9/10 times. any other ideas?

Also another concern that I haven't been able to pin-point, when I turn on my car and I have my head unit volume up about 1/4 or higher, my sub thumps. Pretty sure that isn't normal lol.

lastly, I'm hearing a slight hissing/signal noise out of my front dash speakers. I don't have my RCA's next to a power cable or anything (at least I'm pretty sure). I was told maybe the gain was set to high on my 4 channel amp, so I turned it down, yet it is still the same noise. When I turn up my music loud I can't really hear the noise as much since my music is overpowering it, however if the noise shouldn't be there I'd rather know everything is connected properly and my system is optimum.

Any help on these would be greatly appreciated.

My system is a Polk 880.1 amp wired parallel to the polk mm 10" dvc.
A PA 660.4 powering Polk Mobile Monitors 5 1/4"

[AudioGenics]

curious

what kind of car and model
and mods ?

[Ryan33]

curious

what kind of car and model
and mods ?

Chevy Blazer
& not sure if this helps but Alpine CDA-117 HU

[AudioGenics]

Chevy Blazer
& not sure if this helps but Alpine CDA-117 HU

what year Blazer ?

[Ryan33]

what year blazer ?

1998

[AudioGenics]

I do not know what your background and experience actually is
but my suggestion would be to check out this website
it has a diagnostic flow chart that you can use to determine
specifically and pinpoint the source of noise.

The folks here are really nice too...

http://www.crutchfield.com/Learn/lea..._diagnose.html

[MacLeod]

My first guess is the RCA's. One or more could have a bad ground in it or be otherwise defective.

Disconnect the RCA's from the amp and use a jumper RCA (a single, short cable that simply hooks one end to the left input and the other end to the right) and see if any of the noises are still there.

[evilgenius68]

you have either a ground loop, or you just have a bad ground either at the power or RCA level..I found three ways to counteract this. depending on your situation and what you can deal with..<1>either buy a ground loop isolator and install it, after you make sure your grounds on your audio syatem are clean, well connected and to something other than a dash panel..<2 > do not use the factory grounds for car audio.if possible.. just a variable i tend to like to do away with.<3>.connect all of your grounds of you audio system at the same point, it will take some doing but usually is the least expensive way to rid of the annoyance...that being said . older altenators that have bad windings or are just worn out can cause what you are dealing with, bad engine and body grounds, can cause it also.the equipment you have can also induce such problems..if they have internal issues. isolate where the noise is coming from and deal with accordingly. Hope that helps.

[Vital]

^^^ You just bumped an old thread noone remembers lol.

While we're at it thou, instead of making a new thread - what causes turn on/off "thump"?

I have one every other time when i turn the car off, never when turning the car on. No ground loops, alt while, hissing or whatever else....

[arun1963]

I think its your amp or hu that's causing the popping. You're just hearing it at the speakers. A voltage spike at turn on/off is what you're hearing.

Check both things individually to find the source of the problem.

[Vital]

I did some googling yesterday and found this article.
My "thump" when shutting the car off started around the time i installed Tru SSLD6i line driver. It requires very minimum power so i just connected it to my h/u as power source and remote turn on to my h/u's rt wire which also controlls my amps.
I have a feeling if i re-run that power wire from h/u to the battery like it should have been done to begin with my thump could be solved. If not i'll need to start diggin deeper.

What causes TURN ON/OFF POP and how to cure it:

When a car audio system utilizes additional components such as amplifiers and processors, those devices are turned on and off automatically with a signal from the source unit (known as remote turn-on).

Occasionally, those components may have built in delays that turn them on and off at different intervals. This is especially common when mixing different brands of components into a single system. These different turn on/off intervals may cause an audible "pop" or "thump" when turning the system on or off.

For example, if the amplifier in a system turns on before a crossover, the crossover may send a small transient signal to the amplifier. Because the amplifier is already on, it amplifies the transient signal causing the turn-on noise.

There are different methods to cure a turn-on noise, including devices that "delay" the turn-on of the amplifier until after the other components have come on and "settled down". These delay turn-on devices are available from most car audio accessory suppliers.

To cure a noise at turn-off, the amplifier must shut off before the other components in the system. To do this, you must delay the turn-off of the other components until after the amplifier shuts off.

This sounds like a lot of work to figure out, and it can be frustrating to get rid of such noises, but patience and a little "stick-to-it-iveness" will help you to find the source of your trouble and fix it

[MacLeod]

Could just be the line driver itself. My old Crossfire sub amp had a turn off pop and I had to wire up a turn off delay to keep it from costing me a point everytime I got judged.

[Vital]

Could just be the line driver itself. My old Crossfire sub amp had a turn off pop and I had to wire up a turn off delay to keep it from costing me a point everytime I got judged.

Could you post a link to delay relay/unit/thingy lol?
Just wanna be ready in case rewiring my line driver's power wire will not help

[MacLeod]

You build it yourself. You wire a capacitor to the remote lead of the offending component. Hook the + up to the remote lead and the - up to chassis ground.

This cap will keep the component on for a few seconds (length will depend on value of the cap) and the amp or whatever will stay on for say 30 seconds or so and wont turn off til youre out of the car.

Youll also need to place a small diode in line with the cap but place it before the cap. This will keep the juice from the cap from flowing back thru the remote lead and keeping everything on.

I cant remember what value I used but run down to Radio Shack and buy a handful. Theyre like $1. 10,000 I think is where I started at and it kept it on for 30 seconds I think.

[Vital]

Yeah, it's def line driver as when i disconnect it there's no thump.
I also played around with gains on amps and adjustments on the line driver strictly for tunning and somehow that thump is now barely hearable which leads me to believe that gains have a role to play in it as well, just not sure WHICH gains as i changed all of them lol.