I have every possible electronic noise coming through the audio system!

I used the PC Board-mount from an OEM amp (purchased from another member that opted or an upgrade) to make this harness:



The pinout/wiring is as described in merman's original thread about bypassing the amp.

The signal is carried by Canare L-4E6S "quad star" mic cable. More info about the cable is available here.

The new amp is an Infinity KAPPA FIVE and has differential inputs.

Symptoms:

When I turn the key to the first position, I immediately hear some sort of dimmer/switching power supply noise.

If I turn to the ACC position, I even hear the scratch of the key moving in the switch through the speakers!

If I turn on the climate control, I hear noise from the fan motors picked up and clicks/pops if I manually change the fan speeds.

When I turn on the headlights, I hear noise from the ballasts, and clicks/pops switching between low/high beams.

Then came the alternator whine when I started the engine.

NOTES: If I connect the remote wire to the power input (to keep the amp on all the time) there is far more noise coming through as soon as the HU is turned off. If the amp is on and the input signal harness is removed but the speaker wire harness remains, the system seems silent. I always tested with CD Audio, original media (not a burned disc). This seems like it could be a HU issue, but then why doesn't all this noise come through the stock amp as well?

Attempts to solve:

Checked the impedance/continuity of each connection.

Made sure that there was no connection between any of the signal pins (nothing shorted).

Cleaned up the connections to the grounds under the hood.

Upgraded the power and ground from 8awg to 4awg.

Ran the front channel outputs directly to the door speakers (to make sure the noise source was not the crossover network).

Turned the gains down to about 1/3.

Connected a temporary connection to each and then both of the ground pins coming from the HU harness to the ground point of the amp.

Even tried moving the ground location several times.

I've looked on some other sites and seen references to "big 3 upgrades" - is this really necessary/likely to help when playing music at about the same volume level as the stock amp can deliver? I was going for an improvement in sound quality...

For now, at least its easy to swap the oem back in when the whine gets to annoying/I get sick of blasting the music to overpower the whine...

Has anyone had an issues like this and fixed it?

 

mercman???

CColtsIceHockey??? (your PM box is full)

 

Hi Feuss2,
I got your PM, do you also get hiss? I hear a lot of hiss in the clip you sent.
My PC is on the blink again (thinking of buying a Mac this time) so I haven’t been able to be on the net too much.

Alternator whine is a ground issue, if you are absolutely sure that your amp ground is good then check to be sure that you did not inadvertently ground one or more of you RCA rings. Also check the resistance on each RCA jack (ring) (-) and the system ground with your harness connected and without your harness. Also check the resistance to ground between the amp RCA (pin) (+) and system ground. You should see the exact reading you had on the rings with your harness disconnected. Give the meter a chance to settle.

Let’s see what you get.
Do you have a 2004 non navi?

I’ll remind everyone reading this that while I posted instructions on how to bypass the factory amp it was at first to correct the wrong information originally posted by others. After receiving numerous PMs for help from owners that tried to make their own harnesses (before and after my post) I decided to build one and make it available, it will work noise free every time and you don’t have to cut or splice anything.

Jeff

 

Sounds like you have more noise than anyone i've heard of, so i'd have to say it has something to do with your plug/wiring. I still hear some motor noise. Like I said a while back... The more crap you put between the HU and the amp, the less noise you get. Example, cross overs or EQs,e tc. Good luck. The plug you made looks sweet though.

 

I called Infinity support, and they were really awesome. I wish I had just called them sooner! I sent info regarding the installation from mercman's thread, etc. They gave me some more things to check and try...

One of their suggestions was the same as mercman's above.

I spent quite a bit of time rechecking all the connections. I found:

• No open circuits
• No shorts or inadvertent cross connections
• No deviation from pinout compared to mercman's harness
• Nothing was loose enough to produce an audible change when flexing the wires around the harness or RCA connections

I did a lot of reading about balanced/differential signal transmission with respect to shielding and grounding practices. There is no general rule that applies to everything. The accepted practices differ based on at least 2 factors: The impedance and the frequency range. The possible solutions include:

• Shield to ground on one or both ends
• Resistor between shield and ground on one or both ends
• Shield grounded on one end and connected through a resistor to ground on the other end
• Resistor-Capacitor network(s) connecting the shield to ground
• Connecting the shield to the signal reference on the transmitter side OR receiver side

We know that the stock amp has only a single supply. Inside, I believe castles_saloon found the input stage to have an 8V rail and a 4V "ground" such that the chassis ground could essentially be the negative rail. The input was coupled via capacitors.

I do not know how the balanced line driver on the HU is set up. It would not be unreasonable to think that it is powered in a similar way. If the shield/guard wires are connected to the 4V "ground" for the balanced line driver, this would be a good reason not to ground them.

It's possible that whatever grounding/draining scheme was used for the factory amp, it did not have much consequence as the HU and OEM amp have only a short run of signal carrying line between them and share nearly the same power and ground.

However, in the case of adding 10 feet or so of additional cabling, it's possible that this created a noise receiving antennea that radiated noise into the HU and mixed with the input audio signal before the balanced output stage.

If this was the case, it would not matter how good the noise rejection on the amp was, as the noise you don't want to here is now part of the signal.

I opened the connections where the sheilds connected to the harness. The alternator whine disappeared right away. On the amplifier side, I grounded the sheilds. This seemed to further reduce the other electronic noises that were coming thought the speakers. I had the amp gains turned up high to hear the affects of small changes.

When I turned the gains back down to around 1/3 where I intend to leave them, I hear the slightest noise with the engine and a/c controls off. This is probably the noise floor of the amp. The noise is so low now that I can't distinguish it over the fan on the lowest setting or starting the car, road noise, etc. The new sound is very, very acceptable

It is quite easy to go back and fourth between the new amp and the stock one. I did this a few times for comparison (of both sound quality and to set the rear level properly as I still have stock speakers in the doors.) The improvement that bypassing the stock amp makes is immediately obvious and worth the time and effort!

One unexpected effect of this is noticing that the stock rear door speakers are actually quite decent. They just provide "filler" sound, so upgrading them is not in the immediate plans. With the new amp, they filled in the lows a little better, which the components I have up front were not designed to do (the are best at 80hz and above). I plan on adding a small sub, and I have a 350W RMS output channel on this amp to do so!

I also got to see just how much difference there is when you use the crossover supplied with components vs. bi-amping them. The stock amp has separate channels for the front door speakers and tweeters in the dash. I ran Infinity Kappa Perfect 6.1's without the crossovers for a while because of the way the stock amp was set up. With the proper amount of power and the crossover hooked up, they really sound much better.

I am going to do a few more tests before putting everything back together. If anyone else has some suggestions of things to try that were overlooked or wants to see if this problem could be solved another way, let me know - SOON!

 

-way to go, Sandin!!

 

nice work!!

 

I have a similar case, but cant figure how to get rid of the noise.

Here is my setup:

I'm running only a sub through a 250/1 JL amp. I tapped the REAR balance HU signal at the stock amp. I soldered 6 wires altogether. There is a + - and a drain/gaurd/shield ( I'll refer to it as the shield wire for simplicity) wire. At the JL amp side the shield wire is not connected to anything. I get a high frequecy noise in the REAR door speakers but nothing from the sub.

Attemps to solve:

1. With all the wires tapped i grouned the shield wire. There was still some noise in the system.

2. Cut the shield wire connection so the shield wire is floating. The result was the same with noise still in the system.

3. With the shield wire connection cut, I grounded the shield wire at the front (where the wires are tapped into the stock system). This reduced the noise alot, but there was still some audible noise when i put my ear to the rear speakers.

4. With the shield wire connection cut, I grounded the shield wire at the JL amp. The result was the same as when i grounded the shield wire at the front.

5. With the shield wire connection cut, i grounded the shield wire at both ends. There was still noise in the system.

In addition to the above, i checked the wiring diagram to make sure i tapped the right pinouts and doubled checked to make sure nothing was being shorted.

The bass sounds really good and hits like it should, its just the rear door speakers have some noise now.

Any other suggestions FUESS2?

 

I may be asking a stupid question but do you have any power wires running next to the ground wire (for the 4/8 gage wires)? If so move it. Just incase you havent checked that or didnt know any better.

 

The ground wire is so short that i dont think it matters. Acutually the whole car is ground so it does not matter.

 

A few questions on the setup:

Do you have your input voltage switch set to low?

Are you using a remote wire or the signal sensing feature?

Is the noise hissing, alternator whine or some other electronic sound (like switching power noise), etc?

With the fader set in the middle between the front and rear, is there now a difference in volume between the front and rear speakers? This may indicate that splitting the signal has loaded down the HU too much...

 

The input voltage is set to low and i'm using a 12v remote wire. The noise is hard to explain. It happens without the engine on so i dont think its alternator whine. It is sort of a hissing sound and some other electronic sound switching that goes up and down every now and then.

Have you been able to get rid of 100% of your noise? Im to the point i think i'll just buy a harness from mercman.

 

I had noise that fit that description before, but it was coming through the speakers that were attached to the amp.

Do you have this if you disconnect your RCA connector from the amp side with the car off?

I wonder if this is actually switching power supply noise from either the new amp, or a backlight/dimmer in the car.

It is not gone 100%, but with the volume above 5 or so it really can't be heard enough to realize its still there.

Any time you replace an amp with a higher gain (my new one is 50W RMS/channel for the full range channels) there is likely to be a higher noise floor. You're changing the volume by varying the input signal level from the HU or the input sensitivity (not the amplifier's actual gain). Noises that were present before are unfortunately amplified with the new (higher) gain and therefore more audible. You can minimize this effect by turning the HU a little higher and the input sensativity a little lower. I'm not done trying to see if I can make this quieter. I'm just happy that I've reached an acceptable condition for driving!

Are you using all stock speakers and the stock amp right now and adding a sub? If you bought a harness would you buy a 4ch amp or perhaps replace everything with a 5ch?

It could be that the signal will just not take well to being split. In theory it should work, as the input imedance of the amps are both pretty high.

Before I got the 5ch, I ran the stock amp with a sub and JBL 300.1 Class D subwoofer amp. I found that the speaker level signal going to the rear door speakers (not the 6x9's) worked great, as it does not have that ugly eq stage that the 6x9's do. If you compare the differnce using both as the source signal, I think you'll be surprised how much better the bass sounds when the signal is the same as the rear speakers. You could try this as well...

 

With all this talk about upgrading the "big 3" (Battery to Chassis, Engine to Chassis and Alternator to B+) I found this interesting - even with the grounding strap between the engine and chassis removed from the vehicle with the engine running, there was no increased noise coming through the audio system. This makes me doubt how much good at least one part of this upgrade is...

 

After parking the car for about a week, the next time I started the car I heard all kinds of noise. It wasn't alternator whine or hiss, its actually some squealing static kind of sound. It's really loud!

At the moment, if I remove any 1 of the rca connectors, the noise goes away completely. As soon as I plug in the fourth, I immediately get the noise back. A few times, the noise had shut off after being on for some time. I really have no idea what the source of the noise is.

It does not seem like a bad channel on the amp, because its possible to get clean audio from each channel with just 1 channel out of 4 disconnected.

Does anyone have an idea what would cause this?

Also, it appears as though grounding the shields on the amp makes no impact!