wire size FYI

[chris229 10+ year member]

Originally posted by Steven Another thing chris..

what causes alternator whine. Everyone has always told me a bad ground will cause it. But you seem to think that grounds don't do anything allow a return path for the current.

I've heard bad grounds can cause:

1. alternator whine

2. noise (buzzing or hissing)

3. amplifiers to go into protect mode

forget what you heard----- as these poeple seem t be just passing on things they heard------- over and over again
lets start by saying--------------------- the alternator makes noise ever time the car is runing it is the most noisest thing in the car --------this noise travels all over the chassis and through accesories-------- it has 2 parts the 3000HZ diode chopping and the lower field current

the problem here is that to the poeple who do know ------- it seems that the ground in causing the problem when it really is the bad design of the processor or amp.

let me explain------- when you want to design say a 12v processor or car audio you would want to design it such that---------- no matter what is going on in the power supply ------- noise/ buzzing/ changing states of the ground -------- that NONE of this can get into the audio circuits. The way it is done is by having very high AC-DC impedance[resistance] between the power supply and the audio circuits. As you now high impedance means that it is extremly hard for a current to pass through.

the term of this is called AC-DC power supply isolation and should be i the MEGA ohm range..... Mega ohms are seen as open circuits.

Lets take the case of something everone has heard--------- ground loops------- :

BUT before we go there lets get some things strait------ the only signal ground in the whole system should be the HU----- it ref it to the car's chassis through the ground wire/case/antenna ground and should be 0 ohms----- though ref to a noisy chassis is the worse thing you would want to do---------- but thats what these companies make us do-------- whole different story

current AWAYS wants to find the path of least resistance

well we know that the signal ground is 0 ohms through the HU and RCAs

If an amp/ or anything with low isolation is grounded near a highcurrent path on the car body some of that current will want to path THROUGH the audio circuits and jump on the RCAs to the front of the car and exit the HU. As you can guess ANY current in the signal path will CHANGE the signal

so i ask you----- if you played with your grounds getting the noise to change would you think it was the ground? yea I would too---- and I used too also---- BUT it's NOT it is the bad design letting noise in.

--------To fix it you would need either ground loop isolators------blocks the DC current down the RCAs

------OR put the whole thing on a DC-DC power supply that is high isolation

------ or just happen to find the right ground were not current wants to go though the signal wires-----------very hard----------- this step is were you here people tell others to ground all there stuff to the same point..... trying to eliminate the voltage difference between the audio gear

problems with that--------------------------------------------------

1------- this means ALL grounds would have to be at the same point amps/processors/Hu/ hu case/antenna ground/

2------- even so there are complicated issues on the high current travel through 1 point------ basicly it would still try each path equally------= noise

Without a good amplifier ground the connection is weak and introduces a resistance into the amps power system. As EVERYONE knows resistance = Voltage drop = Loss in amplifier power. This resistance can fluctuate with vibration. A fluctuating resistance will cause the voltage at the amplifier to fluctuate which can introduce alot of noise into the system.

I've seen tests were guys put resistors on the ground and noise noise ever happens----------with high isolation

A weak alternator ground will cause the charging system to be substantially weakened. The Alternator has to work harder to maintain charging voltage and will have a premature death.

alternators are normally grounded through the case-------if it isn't you are correct---------

A weak battery ground - well lets just say this is bad, very bad. It causes slow cranking, more boost starts needed, and our favorite enemy, a voltage drop.

correct again --------though this has nothing to do with noise and you should understand that

Well obviously we don't want any of these, so we tend to make sure all of our grounds are clean, tight, and reliable. ]

but do you see why playing with your ground for a noise problem--------------------- is ---- funny?

 

[maylar 10+ year member]

To be fair, Steven, it DOES sound logical that a wire carrying 100 amps of current COULD produce enough of a magnetic field to induce noise into nearby cables. This is a highly held opinion by many (perhaps most) in the audio world, including equipment manufacturers. The instructions that came with my USX amp specifically warn against it. This is one "myth" that won't go away anytime soon, regardless of how many nay-sayers like chris and myself try to educate the masses.

p.s. Chris, audio cable shielding is quite effective at these frequencies.

 

[Steven 10+ year member]

Thank-you.

Why would manufacturers warn against something if it didn't propose a problem? That would be like warning someone not to jump in the air, because they might be hit by an airplane. NOT GONNA HAPPEN. Manufacturers put these warning in their manuals for a reason

Also, I don't argue to piss people off. I argue to provide an alternate viewpoint. 400 years ago everyone knew the world was flat, but someone challenged that point and proved it wrong. All of the facts that I pointed out are valid, and so are all of yours. We all know what we are talking about, and while you provided so good ponts, I'll still keep running my wires separate, just to be sure.

 

[chris229 10+ year member]

Originally posted by Steven Thank-you.

 

Why would manufacturers warn against something if it didn't propose a problem? That would be like warning someone not to jump in the air, because they might be hit by an airplane. NOT GONNA HAPPEN. Manufacturers put these warning in their manuals for a reason

 

Also, I don't argue to piss people off. I argue to provide an alternate viewpoint. 400 years ago everyone knew the world was flat, but someone challenged that point and proved it wrong. All of the facts that I pointed out are valid, and so are all of yours. We all know what we are talking about, and while you provided so good ponts, I'll still keep running my wires separate, just to be sure.

there is induction----------- just that you would never ever hear it
for one------ at 5A idle current it isn't enough to hear anything

at 100A full full power the REAL signal will drown it out and you could never hear it

 

[chris229 10+ year member]

Originally posted by Steven Thank-you.

 

Why would manufacturers warn against something if it didn't propose a problem? That would be like warning someone not to jump in the air, because they might be hit by an airplane. NOT GONNA HAPPEN. Manufacturers put these warning in their manuals for a reason

 

Also, I don't argue to piss people off. I argue to provide an alternate viewpoint. 400 years ago everyone knew the world was flat, but someone challenged that point and proved it wrong. All of the facts that I pointed out are valid, and so are all of yours. We all know what we are talking about, and while you provided so good ponts, I'll still keep running my wires separate, just to be sure.

don't depend on manufactures to have good advice
they still believe grounds cause noise

they think it's a good idea to run you ground back to the battery

they think class D amps damage subs

 

[chris229 10+ year member]

Originally posted by maylar [

p.s. Chris, audio cable shielding is quite effective at these frequencies. [/b]

says who ------------------ it isn't ---------------------------
find one company who will claim that there little foil wrap can shield low freq EM induction

foil isn't good untill the megahertz range--------- you could wrap a couple whole rolls of foil around your signal cables and it wouldn't be any more effective than paper OR your shirt

you want to do a little test---------------- wrap your signal cables with anything you want than take a second wire and coil some wire around the foil. run 10-20A amps through your noise maker by switching it on and off------for your changing magnetic field

bet you hear noise no matter how much foil you use

while you doing testing

do this test take some small amp/test speaker/ signal source/ and jumper cables

SIGNAL surce must be a walkman or other isolated siganal as a ground loop could cause you to think the power wire is the noise causing thing

lay everything outside your car--------------

connect power to you battery of your car

wire the power into your amp and you signal source

listen wiith the test speaker

play with your power wire------------------------ bet you can't get it to make noise in your test speaker

 

[Steven 10+ year member]

correct me if i'm wrog. But the sheilding in most RCA's is done the same way tv cable is. The center conductor rus down the middle. While the outside conductor is wrapped around the center one. This means the shielding is either coppper, aluminum, or whatever etal the wires are made of. Not foil.

 

[Alaxan 5,000+ posts]

Originally posted by Steven correct me if i'm wrog. But the sheilding in most RCA's is done the same way tv cable is. The center conductor rus down the middle. While the outside conductor is wrapped around the center one. This means the shielding is either coppper, aluminum, or whatever etal the wires are made of. Not foil.

the center wire is the main transmission line for the wire. The second outer wire typically braided is a ground (of sorts and for lack of better easy wording) and does act as a shield. It also helps prevent interference.

 

[maylar 10+ year member]

Originally posted by Steven Thank-you.

 

Why would manufacturers warn against something if it didn't propose a problem

They have to cover for all cases of installer ignorance, including some moron who might wrap his power and audio cables together around the nearest metal post. As we've already agreed, a coil is a bad thing

Also, I don't argue to piss people off. I argue to provide an alternate viewpoint.

Ditto.

I'll still keep running my wires separate, just to be sure.

I hear ya.

 

[chris229 10+ year member]

Originally posted by Alaxan the center wire is the main transmission line for the wire. The second outer wire typically braided is a ground (of sorts and for lack of better easy wording) and does act as a shield. It also helps prevent interference.

you were correct before----- it is simply a ref ground. it isn't a shield and doen't help prevent interference
there are wire company who wrap on or both conductor the coaxial cable with a metal foil--------------- that isn't effective for a car--------- notice I said car

 

[chris229 10+ year member]

Originally posted by Steven correct me if i'm wrog. But the sheilding in most RCA's is done the same way tv cable is. The center conductor rus down the middle. While the outside conductor is wrapped around the center one. This means the shielding is either coppper, aluminum, or whatever etal the wires are made of. Not foil.

if you look at cable TV it has a foil layer to----------------- which is effective in the MHZ range ---1,000,000hz------- NOT------ 3,000hz big difference
think of it this way----------- for sound we know that couple inches of poly fill around you head would dramaticly change the sound of music as it would be killing the high mid--- add trebbe ------------- but you would hear the bass just fine---------- same thing here--------get it ----- it is the freq which matters

 

[maylar 10+ year member]

Originally posted by chris229 you were correct before----- it is simply a ref ground. it isn't a shield and doen't help prevent interference

Absolutely incorrect. Try running your RCA's through twisted pair and see how much noise you pick up. Better still, try it on your home stereo where 60 Hz fields are everywhere. If the shield wasn't effective at audio frequencies we'd be using telephone wire instead - it's cheaper.

 

[chris229 10+ year member]

Originally posted by maylar Absolutely incorrect. Try running your RCA's through twisted pair and see how much noise you pick up. Better still, try it on your home stereo where 60 Hz fields are everywhere. If the shield wasn't effective at audio frequencies we'd be using telephone wire instead - it's cheaper.

it NOT a shield --------- you must study some facts about EMI----------- the purpose of UTP's is --------------------
decrease the loop area------------normal coaxial cables have parrallel conductors and the loop area is -----

distance--between conductors x length = loop area

in a UTP design the loop area is tight ---- closing and opening like----- a bunch of figure eights down the car------ smaller loop area

decrease magnetic coupling------------- in normal coaxial cables the coductors are parrallel to any noise on the car body

in a UTP design------ the twisting acts to put both conductor in a perpendicular path to the noise------- reducing magnetic coupling

to see this simple take a 3" peace of UTP wire lay it on the table in front of you now look at it from the side

you see the each loop puts the conductors going to or away from the parallel table suface

get it----------

 

[chris229 10+ year member]

do you guys really want me to put all the math that tells you you can't easly shield against the type of noise in a car------------? it's very long

 

[Alaxan 5,000+ posts]

Originally posted by chris229 do you guys really want me to put all the math that tells you you can easly shield against the type of noise in a car------------? it's very long

I beleive ya man.... LOL......but u wanna come work some tricks on my truck? I dun have any noise to mention, but can never be too careful LOL