Noise / Whine over connections to amp

[thx1200]

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

[John_H]

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.

[joey17]

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

[piglith]

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.

[PerryA]

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.

[joey17]

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

[sato7]

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.

[joey17]

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?

[Napoleon12]

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.

[joey17]

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