argghhhhh interferance pleaaaaase help.....

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argghhhhh interferance pleaaaaase help.....

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OK, install system couple o days ago...
went to caraudiosecurity, and decided on a vibe blackbox stereo 4, to go with diamond comps, (any complaints don't say them, because i listened to ALL the amps they could put on, and for my price range £150 - £200, it was BY FAR the best, and looks sexy ;) )

OK thats not the problem, i have a carputer courtesy of volxstu, when connected to HU there is HORRIBLE interference, that hums all the time and another one that starts low and increases in pitch the higher the engine revs., thought it was due to me running all cables down one side (lazy lol) so i fixed that, and replaced them with some triple shielded stuff....only to find it did sweet FA.....
sooo i plugged in an mp3 player and it was greatly reduced...i did notice, that if i touched the mini-jack that goes to the HU to the body of the car (IE grounded it) i got exactly the SAME sound as when connected to the carputer.

someone please help, this ATM is a real thorne in my side....lol
 

rorypie

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Maybe it isn't properly earthed? If something is contaminating your car's earth; your stereo would pick up the interference...like when you pick up interference on a radio. Also, perhaps your gear is putting too much drain on power? As your engine speeds up, your alternator speeds up...thus providing more power. I know you get a hum through an underpowered amp, getting deeper as power gets lower (like with some personal tape players...you get a hum when battery's low, worsening as they get more deaded). Of course as your engine spins the alternator faster, the inverse would happen.

I'm not that up on the specifics of car electrics, but if you perform a few tests, like swithing high-beams or fans on to see if it gets worse you may have an answer...it'd be a better way than to find out when your car won't start. If it's not then at least it's one possibility ruled out.

Hope I'm of some help :)
 
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mzhussein
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no matter what electrics are on its always the same sound, when the carpc turns on it generates a new sound lol
how could it be contaminated earth??
ive earth both amps to the bolts that hold the seats down.....different bolt per amp.
 

rorypie

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What are you using? Radio, CD, Cassette?
How are you connecting stuff to the amp? Is it external or internal amp (part of head unit or seperate?). What is a carputer?

(sorry for the barrage of questions...just want to get an idea of what your setup is)
 
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mzhussein
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I'm willing to answer them all if it leads to a solution!!!

OK i will explain top to bottom

i have a carputer (a PC for the car that runs software coupled with a touch screen, very snazzy when it works)
it has a 3.5mm jack output, which goes to a HU, via the AUX input
then the HU has 2 preout, which go to a component amp and to a sub-woofer amp
both of these amps live in the boot, they are both earthed to different places, the power cables and signal cables run down different sides of the car.
all the cable I'm using is suitable for the cause, all power and ground cable is 4awg, the signal cables are triple shielded stuff.

anything else Ive missed out?
 

volxstu

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Earth should be in the same place buddy. Rub down a small section in the spare wheel bay and attach all earths there hence the word ground loop:- multiple earths magnetically attracted to each other through the chassis crossing the path of the signal cables, if my assumptions of GL are correct.
If it still continues earth the HU and Carputer to the same point as the amp Gnd, and if it still continues earth the RCA's.
There are more suggestions that i doubt that you will need i.e turn the gains down, but failing all that you will need to look into another way of carrying signal to the HU. I very much doubt that this would be the problem as people connect MP3 players to HU's all of the time and you arent really doing anything different.
Just out of interest are you using the Gold Plated 3.5mm-RCA.
 
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mzhussein
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ok, this has developed....when i have one AMP (the vibe one) connected its perfect no interferance at all....but as soon as i connect the RCAs to the sub amo i get alternator whine...could this be a dodgey RCA? or a dodgey SUB amp? any suggestions?
 

volxstu

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Oh dear it sounds like your sub amp is sending 12v through the RCA. Try earthing the RCA.
 

volxstu

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These things are usually an instalation issue tbh. Think back to when you installed and uninstalled everything to strip the interior. Did you take out the earth with the power and RCA's still connected?
Still let them know that there is a problem you never know they may help you out.
 
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mzhussein
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nope first thing i did was take the fuses out, cutting the +12 and last hing i did was put fuses back in...its caraudiosecurity, when i go on tuesdya to get exhaust done, there head office is right next to the exhaust place, hows that for convinient :) ill ask them for there opinion...
 
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volxstu

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Nice face to face is all good. They are good people over there. Just make sure your well prepared with the knowledge and remember people will go the extra mile for a nice person. Not that you seem to be the sort of person to go in all guns blazing.
It's a shame I don't think I know anybody who works there any more.
 
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