RCA cable noise

[helotaxi 5,000+ posts]

Possible that the power supply in the HU has an internal bad ground and you're getting switching ripple.

 

[99grandprixGT 5,000+ posts]

do any of you guys know if something like this actully works:

http://www.sonicelectronix.com/item_8179_Monster+Cable+MPC+ISM+201XLN.html

 

[rrmccabe 10+ year member]

Ground loop noise is caused by the alt ripple getting into the signal path because, due to a bad ground, one component in the signal chain grounds through the signal cable to another component in the chain. Not an issue with the car off because the ground current doesn't have the ripple from the alt since the current is coming from the battery not the alt. If grounding the RCA barrel fixes the problem, great, but you have something other than a ground loop issue.

A ground loop problem may pick up alternator noise and usually does, but is not exclusive to alternators. I have had ground loop issues with radio equipment I operate (I have an advanced class amateur radio license) and there this is no alternator involved. Any system including stereos, radios, cable TV, etc can be subject to ground loop when more than one path to ground exist.

Here is the technical description for a ground loop.

What is a ground loop? A ground loop occurs when there is more than one ground connection path between two pieces od equipment. The duplicate ground paths form the equivalent of a loop antenna which very efficiently picks up interference currents. Lead resistance transforms these currents into voltage fluctuations. As a consequence of ground loop induced voltages, the ground reference in the system is no longer a stable potential, so signals ride on the noise.The noise becomes part of the program signal

So anything, including an alternator can introduce noise into a system.

But as you said, as long as it worked. And it did. After reading this forum, I am amazed how common this issue (and fix) is.

 

[helotaxi 5,000+ posts]

A ground loop problem may pick up alternator noise and usually does, but is not exclusive to alternators. I have had ground loop issues with radio equipment I operate (I have an advanced class amateur radio license) and there this is no alternator involved. Any system including stereos, radios, cable TV, etc can be subject to ground loop when more than one path to ground exist.

Nope no alt, but the power supply is AC. There is the noise source.

What is a ground loop? A ground loop occurs when there is more than one ground connection path between two pieces od equipment. The duplicate ground paths form the equivalent of a loop antenna which very efficiently picks up interference currents. Lead resistance transforms these currents into voltage fluctuations. As a consequence of ground loop induced voltages, the ground reference in the system is no longer a stable potential, so signals ride on the noise.The noise becomes part of the program signal

Hum, sounds like what I said...

The problem with comparing like you did is that in the car, the power is DC, noise and the signal are AC. For there to be noise as you describe, there must be a source of AC or ripple on the DC. The ripple usually comes from the alt. If it is present without the car on, the source is something else. That something else is not functioning as it should. You need to find the problem, the noise may be symptom of something more serious.

 

[rrmccabe 10+ year member]

Nope no alt, but the power supply is AC. There is the noise source.

Hum, sounds like what I said...

The problem with comparing like you did is that in the car, the power is DC, noise and the signal are AC. For there to be noise as you describe, there must be a source of AC or ripple on the DC. The ripple usually comes from the alt. If it is present without the car on, the source is something else. That something else is not functioning as it should. You need to find the problem, the noise may be symptom of something more serious.

I agree that "The ripple usually comes from the alt". But I dont think there is a problem elsewhere.

There are hundreds of threads on this site about users grounding the RCAs at the head unit and noise going away.

I am really surprised that the RCAs on the head unit are not at ground anyway.

I am pretty sure my noise was computer related. From the body control module or something. I would get it when the dome was dimming (theater lighting) etc.

All is good now. Regardless of what was making the noise.

Thanks for you help.

 

[onecoolee]

As an EE and former USAC/IASCA competitor and part-time car audio installer, I have seen ground loop issues many, MANY times. To be completely honest, they aren't always easy to avoid. Think about it... most installs are simple--consisting of a head unit and amplifier(s)... I have rarely seen ground lopp issues in these installs, but they can still exisit. Most installers do not use the same ground point for the head unit and ampliefiers, which is really the easiest way to avoid a ground loop. The entire chassis of the vehicle is ground, BUT, there are differences in potential all over the place...

A complex install might consist of a headunit, 2 or 3 signal processors or an EQ/xover, and amps--all of which are probably grounded to different locations on the chassis... this type of instlal is always subject to noise issues... some of which may be pops, clicks, buzzes, alt whine, etc. If the ground point is not the same for every piece of equipment, its best to make sure that there are not huge differences in potential between ground points... you can do this by take an ohm meter and setting it to the 20 ohms scale, and making sure that the only difference in resisitance that the meter is reading is within the leads... touch both leads together and it will read like 0.8 ohms. Then, touch the head unit ground point with 1 lead, and the singal processor ground point (Or amp ground point) with the other lead... there should be the same reading as if you touched the 2 leads together... that means that there is no major resisitve change in the ground point from the head unit to the signal processor or amplifier ground point, and thus there should be no difference in potential either. You can also measure the resistance from each ground point directly back the ground post on the battery, and both points should yield the same result.

By doing this, there aren't any ways for noise to sneak into the system and ride on the signal lines like its explained above. Induced noise can happen too, but that easily avoided by keeping your speaker and RCA lines away from noises components, like underdash computers, and any other lines that may be emitting an AC inductive signal which can couple itself to an adjacent line. Try to cross lines with fluctuating voltage at a 90 degree angle to reduce the amount of coupling between their paths.

Components in general, if poorly designed, can cause huge issues with noise problems... in car audio, like most everyhting in the world, you get what you pay for, and an el cheapo amp, with a poorly designed power supply, can make the signal side of the amp noisy... the same goes for EQs, and other processors. Plus the more processors you put in series, will only amplify your noise, as soon as noise is prevalent within the system. So watch your gains too and set them properly being sure that you aren't boosting noise, or clipping the good signal in your system... if you bump up your gains too high, you are amplifying the signal with the noise component in it, which can make an expensive system sound terrible. So, proper tuning can make a system sound great, and can clean up the noise too...

Another means of avoiding noise is by using a high volt output head unit (4V+), or a signal processor which will amplify the signal voltage before noise is on the signal lines...then this elevated signal strength is fed to processors or your amp(s), as a higher level (or higher effective gain), and thus a cleaner signal. This allows you to use less gain on your amps, because the signal being sent to them is already boosted... and the amp isn't having to amplify the signal; plus the noise on the line. Most good headunits output at least 2volts these days, and some do 4V or higher, which always helps.

Good quality RCA cables are important too... don't buy a $1000 amp and a $3 single shielded RCA cable... if you can afford the expensive amp, buy a decent cable too--something with dual shielding or even twisted pair signal transmission to avoid noise issues... yes, twisted pair cables can help... since the noise can effectively cancel itself out in this configuration. BE careful where and how you run your RCAs too... induced noise is easy to get into a system if you aren't careful where the RCAs are run. Always be sure that the jacket of the cable is not pierced or touching ground... Grounding the RCAs signal shield to the car is an immediate source for MEGANOISE ! You will know if this is your problem in most cases...

A good installer will do all of the above, making sure to minimize and noise issues. By following good grounding practices, using properly designed equipment, and good RCA cables that are run in a manner to avoid induced noise, alot of the issues being discussed in this thread are easily avoidable.

 

[onecoolee]

Yea sounds like computer noise to me. Something "synthetic".
It is running along a factory loom which might be the factory Bose amp which I am still using for Onstar.

I see that Pioneer has ground loop issues from reading post here. I might try grounding the RCA at the head unit.

try turning your gains down too... when you have this so called "synthetic" noise, it is being generated by the DC components in your vehicle (due to DC switching on and off). USually this can be avoided by making sure that your amp is not amplifying a crappy signal. Making sure that your RCAs are carefully routed away from compujters and away from most stuff under your dash. Plus, use good RCA cables too...

If you are using a factory headunit, which always has low signal level outputs, the problem you are experiencing will most likely always be there... factory HUs ****, and don't interface well to aftermarket stereo equipment. If you are using an aftermarket HU, in your basic, Headunit/amplifier configuration, as long as your gains on the amp aren't set too high, you should have no noise.

 

[rrmccabe 10+ year member]

^^^

Good info and thanks !

I am using a Pioneer Z2. So the factory head unit is gone.

It gets tougher all the time. There are modules everywhere in new vehicles. Onstar, heated seats, opra lighting, etc.

I have 4 guage power on left of vehicle and preamp cables on the right. Both sides have looms under the sill plate going to the back. I know its not good to run cables parallel if you can because of coupling which can lead to interference. But hard to run to the back without sharing some space with other wires.

Mine is pretty quiet now with the except of a noise I pick up when my seats get warm and start to cycle the t-stat.

I ran two 14 guage wires to the back for backup light (camera) and amp remote. I almost wish I ran a 3rd and ground the headunit with the amp ! Guess its not too late.

 

[Kriszilla 10+ year member]

It's the Pioneer SMD fuse issue. I have the Exact Same Thing. Make sure that you never, ever hotswap the RCA's while the deck is on.

If you plug / unplug the RCA's while the deck is on you can blow the SMD fuse and it's going to become synthetic noise city in your vehicle. Grounding the RCA's helps, but doesn't eliminate it. The SMD fuse has to be repaired, or replaced with a 1 watt 1/4 ohm resistor.

 

[XxSuperAdamxX 10+ year member]

I got RCA noise too. It seems like the metal part of the RCA is touching each other creating some weird noise. I turn off my subwoofer it doesn't have a static or distortion noise on my rear left speaker, but once I turn on my subwoofer...the rear left speaker goes weird. Yeah...I think pioneer does have that stupid ground loop that's unavoidable.

 

[rrmccabe 10+ year member]

It's the Pioneer SMD fuse issue. I have the Exact Same Thing. Make sure that you never, ever hotswap the RCA's while the deck is on.
If you plug / unplug the RCA's while the deck is on you can blow the SMD fuse and it's going to become synthetic noise city in your vehicle. Grounding the RCA's helps, but doesn't eliminate it. The SMD fuse has to be repaired, or replaced with a 1 watt 1/4 ohm resistor.

Thansk for info. Mine is 100% silent with the a grounded RCA (just one) and I sent my adapter to two friends and it fixed theirs as well.

I am pretty sure you are right about the SMD. They must be really sensitive.

Rich

 

[Gohar ali]

HI, same problem of noise i found before in my car too but i got the solution i found one RCA noise filter from pioneer shop better try once hope problrm will solved connect it wth RCA cable and other end connect to your power amp. ( sometime this type of noise generate by electical problem in vehicle )