[makkan00]

Hi,
I have E90 and after reading sticky sections, I have upgraded my sound system.

Following is my steup up;
HU (coded to hi-fi i.e 5v) --> From front speakers --> RCA convertor (2 channels, all coming from front channels)--> Kenwood Amplifier (KAC-7405) --> 4 channels output --> a) 2 to SWS-8s and b) 2 to Front components.
Rears are connected directly to HU (same as apline upgrade).

My connections:
Positive cable = from battery with inline fuse
Negative: Earth terminal of E90 (rear right side) as suggested in the forums or can be fitted to rear left side.
Kit: 8 Guage

My problem:
HU is off:
When key is inserted and you press START button without pressing the clutch, and car goes into ignition mode, noise appears from the front speakers. (listen to audio clip please) This is ticking noise which disappears after 4-5 seconds.
If I disconnect RCA to amp connection, I can hear that this ticking noise is coming from under the hood / bonnet of the car. With amp connected, it travels through the sound system.

And When I start the car, there is constant noise which increases with the engine RPM. (HU is still off)

If I turn on the HU, this noise is still there but over- shadowed by the music.

When I was coding my car the other day, this sound increased dramatically, and gave me impression that it was related to some module of E90.

I had JBL amplifier previously, which was quieter compared to Kenwood amplifier, however JBL also had some noise.

I have already purchased noise suppressor filter and waiting for its delivery.

Few changes and findings:
I have changed RCA cables, and going to change RCA convertor as well.
At the moment my amplifier is fitted where apline kit amplifier sits, but my plan is to shift it to place where CD changer sits.

I have also tried connecting earth cable to 2 screws which are next to, where apline amp goes, and result: humming noise increases. I could not connect earth directly to battery as my earth wire is not long enough.


I wonder if somebody can suggest what else should I do to get rid of this.

N.B: This sound clip starts when key is inserted, and when I press start button without pressing clutch/ brake and ticking noise appears (start of sound clip)

Also listen to the noise which appears with engine RPM (later part of sound clip)

Any solutions / suggestions / corrections welcome.

Noise clip




[Edit:]
Followings have been changes and no avail.
1- RCA convertor changed to two different brands, active and passive but no luck.
2- RCA cables changed to different make but no avail.
3- Negative wires of amp has been connected to Right, Left earth junctions
and directly to battery negative terminal but no luck.
4- Noise isolator which connect to positive terminal of battery failed.
5- Noise isolator which connect to RCA connetoers has failed as well.
5- Remote wire has been connected directly to battery to see if that is culprit but no luck
6- Connected amplifier to external source (iphone) through RCA cables and sound disappeared.

[makkan00]

Any takers on this?

[ctuna]

http://www.e90post.com/forums/showth...ighlight=noise

Do a search with the word noise in it a lot of stuff will pop up.

http://www.e90post.com/forums/showthread.php?t=641323

[makkan00]

Originally Posted by ctuna

http://www.e90post.com/forums/showth...ighlight=noise

Do a search with the work noise in it a lot of stuff will pop up.

http://www.e90post.com/forums/showthread.php?t=641323

I have read plenty of threads on this:
Recommendations are;
1- Change ground cable, which I have done it, except I did not try connecting earth directly to battery.
2- change rca adaptor. Done that, and bought different model / make of RCA convertor but no benefit.
Any other solutions?

[Rong335i]

With the RCA disconnected, if you were to turn the gain to 0 and then max it does the noise stay in the same level?

Do you have a second car where you can try to do a quick install to see if its the amp itself?

[makkan00]

Originally Posted by Rong335i

With the RCA disconnected, if you were to turn the gain to 0 and then max it does the noise stay in the same level?

Thanks for your input. I will try it, and will get back to you.

Originally Posted by Rong335i

Do you have a second car where you can try to do a quick install to see if its the amp itself?

No I do not have access to another car. I had JBL amplifier previously, which also had noise but less compared to Kenwood (I guess Kenwood is more sensitive or less watts, so I had to increase gain more on kenwood and hence noise is more).
It makes me think that;
1- Noise is coming from the interaction of some modules to amp or wiring, as duing coding this noise has gone to max, and when coding was finished, it returned to normal levels.
2- Noise may be coming due to lack of amperes at designated earth points.
3- Noise, possibly from positive terminal.

I cannot resolve point 1.
About 2, I can try connecting earth directly to battery.
About 3, noise cancellor is on its way.

However mean while I will try to find answer for your first question.

[makkan00]

Originally Posted by Rong335i

With the RCA disconnected, if you were to turn the gain to 0 and then max it does the noise stay in the same level?

Do you have a second car where you can try to do a quick install to see if its the amp itself?

Hi,
As soon as I disconnect RCA, no more noise.
I have increased the gain to max and 0, and no noise at all with RCA disconnected. As soon as RCA is connected, sound is back.

What I can see that when I turn the car into ignition mode, there is some clicking noise coming from the front of car (under the hood). If RCA cables are connected, that noise is amplified.

I have changed RCA cables to different one but no benefit.
I have also changed RCA convertor but no benefit.

Sounds like sound is coming from headunit, however rear speakers are fine.

I have taken the input from OEM subs plugs and wires goes all the way to trunk, where they go to RCA convertor ---> amp.

Any suggestion what other things should I consider?

I have already ordered noise cancellor and awaiting delivery.

Thanks.

[Rong335i]

Is your RCA converter designed to convert the differential output to single ended? Is it an active or passive converter? It may be your converter.

On my other car, I had failed experience when I tried to use a passive Schoshe converter. At the end of that project, I just replaced the HU to a Kenwood with RCA out and ended it there.

The second time around, I just got the JL amps with diff input for my HiFi system and avoided all converters.

Maybe a member who has success using a RCA converter can chime in and let you know what brand of converter they used.

[kaigoss69]

Make sure with the ground cable connection at the amp, that the cable does not run near the RCAs, especially near any of the RCA plugs at the amp.

[everlast]

I'm thinking its the converter... the signal coming from the HU is balanced and maybe these converters are not compatible.

[makkan00]

Originally Posted by Rong335i

Is your RCA converter designed to convert the differential output to single ended? Is it an active or passive converter? It may be your converter.

On my other car, I had failed experience when I tried to use a passive Schoshe converter. At the end of that project, I just replaced the HU to a Kenwood with RCA out and ended it there.

The second time around, I just got the JL amps with diff input for my HiFi system and avoided all converters.

Maybe a member who has success using a RCA converter can chime in and let you know what brand of converter they used.

Thanks. I started with active convertor which takes positive from the battery and negative form earth. It did the job but I thought it was culprit.
I asked the manufacturers, and they sent me another piece but still same complaint.

Later I bought passive convertor and that is even worst than active one.
So I have gone back to active one.

I am waiting for noise cancellor which goes b/w battery and amp. Keeping my fingers crossed to see if that works.
Other ideas is to connect earth directly to battery to see if that make any difference, as this has been suggested by manufacturer of active convertor.

Originally Posted by kaigoss69

Make sure with the ground cable connection at the amp, that the cable does not run near the RCAs, especially near any of the RCA plugs at the amp.

Thanks mate. At the moment ground cable is away from RCA cables, but next to output cables which are going to sub (as power cables and output cables are on same side of amplifier).

I will double check that.

Originally Posted by everlast

I'm thinking its the converter... the signal coming from the HU is balanced and maybe these converters are not compatible.

Thanks for your input mate. I have changed RCA convertor to second one by same manufacturer and later to passive one as mentioned in my previous post, but no luck.

[cdgatti]

I am wondering if that amp will properly process the differential balanced inputs? When I was looking for an amp I crossed that one off the list because I couldn't comfirm compatibility. The list I found was fairly short that would accept the BMW differential balanced inputs. JL Audio, Arc, Zapco, some Alpine and some Soundstream.

[makkan00]

Originally Posted by cdgatti

I am wondering if that amp will properly process the differential balanced inputs? When I was looking for an amp I crossed that one off the list because I couldn't comfirm compatibility. The list I found was fairly short that would accept the BMW differential balanced inputs. JL Audio, Arc, Zapco, some Alpine and some Soundstream.

If we use RCA convertor which converts signals to low level, is that not enough.

My HU is already coded to Hi-fi, so I am having low level balanced output from my HU, which goes to RCA convertor ---> Amplifier.

Am I not correct

[ctuna]

The balanced (differential ) Inputs on some of the amps mentioned along
with the same kind of output from the stock Head Unit is a noise canceling mechanism.

[makkan00]

Originally Posted by ctuna

The balanced (differential ) Inputs on some of the amps mentioned along
with the same kind of output from the stock Head Unit is a noise canceling mechanism.

?
Can you kindly elaborate before I take any wrong conclusions from this statement?
Thanks.

[ctuna]

http://en.wikipedia.org/wiki/Balanced_audio

[everlast]

Can you list the brands / models of the RCA converter you used? Maybe we can help clear this up with that info. Many RCA converters are intended to convert speaker line to unbalanced line level, not balanced to unbalanced.. So the problem may still be with the converter.

[makkan00]

Ok Guys, followings have been done to rule out the noise:
1- Changed RCA convertor
First convertor with inbuilt remote wire function
Second convertor
Unfortunately UK audio market has few options of RCA convertors. If you have any better in mind which can be sourced in UK, please feel free to mention.
If not, then I may have to source from states / europe.
It appears that sound is not coming from this, as changing RCA has not made any difference.

2- Connected earth directly to battery, no effect.
3- Connected remote wire directly to battery, just to see if it was getting less amperes, no effect.

Engine noise suppressor ordered and still waiting for its delivery.

I coded few modules in my car today, and this noise increased when I was coding FRM module. To me it seems like, there are two things

a) When car is on ignition mode, initial clicking is from interaction of module (possibly FRM) to HU / wires.
b) Engine noise coming in when car is on (awaiting noise suppressor).

Any suggestions?

[everlast]

It's the RCA converter. Neither of those are correct. They both convert speaker level to line level. You should be converting balanced line level to unbalanced line level.

This is an auction for a VEN4, used to be the "go to" box for BMW line level conversion in the day.

http://www.ebay.com/itm/Peripheral-I...#ht_500wt_1344

Technically you should be looking for a "balun". The ones you're using don't isolate the ground from the signal, so any electronically noisy event (like coding) will increase the noise heard on the amp. Another element is that the ones you're using are designed to take speaker level voltage down to line level, which means you're the output from them coming from the HU, stepped down, would be very low. You'd have to have the gain up quite high, and the signal to noise ratio at that point would be terrible.

[makkan00]

Originally Posted by everlast

It's the RCA converter. Neither of those are correct. They both convert speaker level to line level. You should be converting balanced line level to unbalanced line level.

This is an auction for a VEN4, used to be the "go to" box for BMW line level conversion in the day.

http://www.ebay.com/itm/Peripheral-I...#ht_500wt_1344

Technically you should be looking for a "balun". The ones you're using don't isolate the ground from the signal, so any electronically noisy event (like coding) will increase the noise heard on the amp. Another element is that the ones you're using are designed to take speaker level voltage down to line level, which means you're the output from them coming from the HU, stepped down, would be very low. You'd have to have the gain up quite high, and the signal to noise ratio at that point would be terrible.

Thanks. I have sent message to seller to find out if he is willing to ship it to UK.

Wondering is THIS any good?

Thanks.

[makkan00]

Originally Posted by makkan00

Thanks. I have sent message to seller to find out if he is willing to ship it to UK.

Wondering is THIS any good?

Thanks.

Ok, I have ordered VEN4. Since it is coming from states, it will take time to arrive to UK.

For the time being, I bought noise isolator shown up in the link and also noise isolator which goes with battery positive wire, but both of them failed to rectify issue.


Reading from here

The OEM audio signal is a ‘floating’ signal ground in most cases, particularly any time it’s out of the head unit or amplifier powering a speaker directly. Even the signals between the head unit and amplifier are often still ‘floating’ signal grounds that could power a speaker in a non-amplified model. This simply means the OEM signal has a separate signal negative (-) for the left and right channels as you’d expect is normal with any powered output that directly drives a speaker. The problem is that many times, the preamp level RCA inputs of an aftermarket device use single ended ‘common’ signal ground circuitry where the outer shield of the RCA inputs are electrically tied together and only the center pin of the RCA (the positive signal) is separate from left to right. This means even if the audio signal voltage levels are compatible with an amplifier’s input signal range, the signal grounding may not be.

Certain amplifiers and processors available today have fully isolated preamp level input signal grounds (both from left to right and from the negative chassis ground of the device’s power supply), but it’s not an across the board rule of thumb. You have to check the device – easily done with a DMM – to be sure.

Isolation between left and right signal grounds is important, but one of the big important considerations (whether aftermarket or OEM head units) is that signal processors and amplifiers have a high degree of isolation between any signal reference ground and the negative electrical connection at the device’s power supply inputs. Whenever there is a low resistance between power supply and signal grounds, you’re asking for a noise problem via ground loops.


Reading this, I guess I am having noise via ground loops.

Can anybody please suggest a way to deal with this?
My interventions and efforts are exhausting now....

[ctuna]

I would be trying the known to work amps with this car.
Like JL audio . These require no interface devices to work noise
free as they are designed to work with the kind of signals the head unit
puts out.