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Discussion Starter #1 (Edited)
Hello! I have been a lurker for a while, but now that my 2009 Carbio came in last week, I spent the better part of this weekend installing a new stereo system and I am having an annoying little problem that I hope somebody might have a recommendation for.

First, a little about my system. I'm using a Sony BT-2700 head unit (integrated bluetooth), an Orion XTR5004 amplifier, a pair of Orion XTR652 door speakers, and the JL Audio sub + enclosure available from 4smartcar.com. It sounds absolutely amazing! The sub isn't super deep (I'm coming from a truck with two 15s, so my perspective is a little warped), but it's well-balanced and the system as a whole kicks really hard with no distortion. I'm especially impressed with as low as the 652s go, providing ample tight mid-bass in the Smart door and preventing the need to set the crossover higher on the sub.

The amp is mounted behind the passenger seat. All cables are run under the carpet on the passenger side of the car. The power cable and turn-on cable are toward the center of the car, whereas the RCAs and speaker wire are run on the side closer to the door. The separation is intended to prevent "alternator whine" where you pick up frequencies from the power cable in the RCA cables.

Anyway, about my problem. I'm picking up some noise through the system. It's not alternator whine. It's a very digital/harsh sound and very high pitched. Head unit volume does not affect the loudness of the sound, so it's definitely post-head unit in origin. This also did not happen until I hooked up my amp. While driving, shifting gears seems to cause the signal to chatter (a fuzzier "modem" like sound), but you sometimes get the chatter and squeeking at other more random intervals.

I am hypothesizing that what I'm hearing is actually digital chatter between the Smart's computer and the control systems in the car (like shifting, gas, brake, wipers, status lights, headlights, etc.). The only other thing I've experienced that sounds similar to this was when I was wiring an old studio of mine and I had an audio cable too near a SCSI cable.

So my question is this... First, has anybody else experienced this? Second, if so, how do I go about getting rid of this noise? I am currently using pretty average RCA cables (not bad quality), and I thought about maybe getting Monster or something that is "directional" (shielded and grounded only on one side), but before I plop down a lot of money on Monster, I wanted to make sure that better shielding would even help. RCA, being unbalanced, does not provide much in the way of RF shielding, even on expensive cables. Do I need a more exotic solution, such as lining part of the floor with Mumetal or some other material that blocks radio interference? Does anybody know exactly what parts of the car are "loud" with digital signals that I should avoid?

Any help is appreciated!

Links to my modding experiences thus far...
Modding My Smart: Stereo System, Part 1 - Avian Waves : Blog
Modding My Smart: Stereo System, Part 2 - Avian Waves : Blog
 

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Is your amplifier in a metal case? If not (plastic enclosure) try shielding the box with as little protection as aluminum foil to see if this makes a difference; if a change is noticed but the interference still great, a better enclosure might be warranted.

You could try adding ferrites to the power and/or the audio input cables to the amplifier. Radio frequency interference - while well beyond audio frequencies - tend to rectify themselves into much lower inputs, providing unexpected offsets. Ferrites block RF without affecting audio. You can find both clamp-on and whole ferrites that you feed the wires through.
 

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i no what it is trust me. your signal wire the very skinny one that goes to your deck or head unit to your amp is to close to the power wire. if you rout it away from the power wire it will be fine and no whine :)
 

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It is a ground fault loop. Some where you have a bad ground. Maybe a cell phone also from how you describe. There is nothing you can do but turn off a cell phone.
 

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You may be right about cables with better shielding and also the suggestion offered on shielding the amp. You mentioned a cable routed along the center console and noise associated with shifting which does seem to support your "digital chatter" theory. Can you reroute that cable?

If you can find a wiring diagram, it might help you locate where the data-carrying wiring is running and you can stay away from that. With a car this small, there probably aren't many places that don't have some sort of wiring nearby.
 

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i dont mean to be rude but this is what i do sound systems installs tuning and anything els you can think of. at least 20 people come to me in a year giveing me the same story it will prob wind up as the rpms go up all you have to do is put the power wire from your batter to amp on one side and your signal wire on the other side of your car. i think the battery is on the passenger side (dont have smart car yet) so wrout the power wire down that side of the car close to the dore pannels and wrout the signal on the dirver side close to the dore pannels. pm me after you have done this trust me it will work its called alternator wind the signal wire picks up the fq's of the alternator and scince the power wire is conected to the battery wcich is conected to the alt well you get it.

joe
 

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Joey, READ what he said... it is NOT alternator whine...

THX, try temporarily running another RCA above the carpeted areas to the amp and see if when you move it to the center console it has the chatter you talk about. Also verify your ground connections are clean.
 

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im sorry i read the post a long time ago and forgot about that. as for the chattering is this a new amp or an older one that kind of got beat up or somthing where the rca cables are moveing up and down in the amp or somthing like that in other words is everything nice and tight and no wiggeling or anything of that nature?
 

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reading joey17's posts i am lost. did you get the prob fixed. not knocking joey17, but if u do (sound systems installs tuning and anything els you can think of) you should know how to troubleshoot system noise.
 

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i do for the most part its just kind of hard when i cant here it or look over the wireing. but as i said in my last post check the rca cables and make sure there in there good and not bouncing around and if you could, could you get us a vid
 

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Discussion Starter #11
Sorry for not replying in so long. I subscribed to this thread but got absolutely no emails, so I thought nobody had any help. :p Let me address each issue and also update one what I've found. Thanks EVERYBODY for the tips! This has been a most interesting read!!

John H - The amp is in a very thick and heavy metal case. It's an Orion XTR5004. Orion makes REALLY good stuff. I've been brand loyal for 15 years. :-D It's sitting up against the engine compartment, behind the passenger seat, but I have moved it around to different positions - no change.

Joey - If by the skinny wire, you mean the amp turn-on wire, then yes, it is run down the same "channel" under the carpet as the power wire. I'll try moving it to the side of the RCA cables. I should note the RCA is over two feet away from the power wire, which I know is recommended. Also, the "chatter" is still audible even when the RCAs are unplugged.

piglith - It may be a ground loop, but it's not digital cell phone chatter. I can enduce the digital chatter by moving the shifter from N to D and back. It's exact and always happens when I do that. It happens at other random intervals, which is how I inferred the possibility that other aspects of the Smart's control systems may chatter themselves. I am very convinced the chatter is due to a data bus that the Smart uses and not something like a cell phone or other external factor.

PerryA - If anybody can dig up a wiring diagram, that'd be so awesome. I am not using shielded (coaxial style) RCA cables. I'm using twisted pair style, which from what I've read, is better at reducing noise than shielded RCA. For the heck of it, I tried a coaxial RCA cable and had the same results.

Now for updates... Maybe somebody will have other ideas?

1. I ran my head unit's ground to the same grounding point as my amp. I'm using the bolt that's sticking out over the engine compartment carpet. (It's bare metal and a resistence reading with a voltmeter showed it to be a good ground.) This reduced the noise somewhat. Also, it seemed I did have a little alternator whine afterall initially, but it wasn't much as I only noticed it when it was gone, not when it was on. :) Anyway, the digital chatter is still there, but it is less.

2. As stated above, I've tried various RCAs with no difference.

Some thoughts...

I'm thinking that the sound is either leaking in through the ground point or the power cable itself.

The ferrite is an excellent idea. I'm going to try wrapping it around the power and ground wires. Does it matter where I place it? At the end I would assume... Both ends maybe?

I wonder if 4 AWG wire would help? (currently using 8 AWG Monster)

Does anybody else have a good suggestion for a ground point? Would it be safe to run the ground for the amp directly to the battery? Afterall, in a Smart, that's a pretty short path (less than three feet from where my amp is now)! Could a direct battery ground be noiser? I read somewhere that direct battery grounds can sometimes be noisey.

Matching the head unit and amp ground to the same point is a start, but I'm not finished! :)
 

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The ferrite is an excellent idea. I'm going to try wrapping it around the power and ground wires. Does it matter where I place it? At the end I would assume... Both ends maybe?
Glad you came back to check!

The ferrite is most effective at the entry to your amp. If you've already unplugged the inputs and you still hear the whine, then you only need to concentrate on the power and the speaker cables, not the inputs (at this point, at least). The noise on any entry into the amplifier can cause problems on the input circuit. The ferrites will cut the noise down as the wires pass through the center; the closer they are to the amp the less possibility you have of introducing more noise.

Your speakers are completely isolated from the car ground, right?

Good luck!
 

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Discussion Starter #13
Glad you came back to check!

The ferrite is most effective at the entry to your amp. If you've already unplugged the inputs and you still hear the whine, ...
The whine/digital distortion is still there when the RCAs are unplugged, BUT it's quieter. Does that mean anything?

...then you only need to concentrate on the power and the speaker cables, not the inputs (at this point, at least). The noise on any entry into the amplifier can cause problems on the input circuit. The ferrites will cut the noise down as the wires pass through the center; the closer they are to the amp the less possibility you have of introducing more noise.
Thanks for the tip. I ordered a couple different ferrites and I'm going to try them on different cables one at a time to see what happens.

Your speakers are completely isolated from the car ground, right?
Good luck!
I would imagine so because the mounting area in the doors is completely plastic. The only way an electrical ground could be made on the speakers there would be over the speaker wire, which would introduce a lot of analog distortion, which I don't have, not to mention it'd make my amp hot and unhappy from the short. ;-)

Since my last post, I have done the following:

- Replaced the 8 AWG amp ground with 4 AWG ground.
- Grounded the amp directly to the battery (along with the head unit's ground).

Neither had any effect, but the wiring is a lot cleaner looking going to the battery instead of the bolt in the luggage area.

Oh before anybody complains about grounding to the battery, there is nothing electrically wrong with it in a smart because the ground cable is still really short since the battery is in the foot well. Additionally, there is no noise increase from my doing that. It can be noisier, especially with a LONG cable in a typical car. If I was starting with that set up, I would definitely try a different grounding point first before posting. Anyway, just wanted to clear that up because I can already hear somebody fixing to type "don't ground to battery - NOISEY!" :-D
 

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did you rout any of the cables down the center of the car you didd mention when you shift the shifter it does it. maybe the wires are being disrupted when you shift or when you drive. does is still do it when ur not moveing?
 

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just upgraded my system, I have the same problem too:confused:

everytime I put I foot on the gas paddle the sound became louder.......

what should I do ?
 

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Trying to think outside the box... how is your amp attached to the car? it could be introducing noise that way if you bolted it to metal... a grounded part!
another possible noise leak could be the Blue wire (amp on 12v) try disconnecting it and using a 12v external input to turn the amp on.. hey it might be a dirty 12v from the radio...
 

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Discussion Starter #18
just upgraded my system, I have the same problem too:confused:

everytime I put I foot on the gas paddle the sound became louder.......

what should I do ?

Your problem sounds like classic 'alternator whine" -- especially since it gets louder as you accelerate. I'll guess it also changes pitch as you accelerate and when the car shifts.

Do a google for "alternator whine" and you will find a bazillion troubleshooting guides.

As for my original problem. Here's how I resolved it (sorry I never replied to this post).

1. I moved the amp to under the passenger seat, instead of leaning against the engine compartment. A lot of the noise was being directly induced in the amp, but I couldn't hear it until I plugged in the RCAs. I'm guessing it's a combination of induction noise from computer cables with a ground loop here. I'm not sure. Again, my issue was "digital chatter" and not plain old engine whine. This eliminated about 50% of the noise.

2. I turned up the pre-amp on my head unit and turned down the gain on the amp. This eliminated about 25% more noise.

3. I installed an RCA noise filter (magnetically coupled) with the coupling as close to the amp as possible. I was then free to run the RCA any way I wanted, because any inducted noise on the RCA would be eliminated at that point. I was shocked at how good these things sound now. In the past, you would hear a perceptible drop in high frequencies. I A/Bed this thing (just a generic one I got at a local car stereo shop) and I can't tell the difference. Good enough for me. I could probably undo step #2, but I just haven't gotten around to it.

For those looking, here's a bunch...
rca noise filter - Google Product Search

One thing I didn't try, but was planning to if #3 didn't work was pulling up the carpet on the passenger side near the amp (under the seat and towards the engine compartment) and lining it with mumetal or some other similar RF shield. I've had good luck eliminating A/C whine (of the 60Hz variety) with that stuff before.
 
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