. (see last post this post is now no longer relivant)

 

I have a noise problem. I cut every single wire in my harness (not the car's, the aftermarket one), ran 12v from the battery, etc to try to find out what it is.

As a last ditch thing I plugged the rca's into just the head. This produced no noise. I connected ground to the head with noting else connected and I got noise. I ran a ground straight from the negative post on the batter to the head and I still got noise (again with nothing else connected). The noise is only present with the car on.

Unplugging the alternator and making it run on battery gives me a rapid clicking sound, running with the alternator gives me alternator whine.

The nose isn't loud but it's defantly there.

Ideas?

Head is an alpine. Amp is an infinity.

 

If you gave the head a very good ground, then it sounds like a bad head...I typically run the HU ground into the factory wiring, but I also "T" off the ground wire and bolt it somewhere on the firewall. Could also be one of those heads with a funky preout level setting that only sounds good boosted at the head via the internal controls.

 

What do you mean boosted via the internal controls? The only way I know of to boost the signal is to crank the volume.

The head is an Alpine CDA-9833 that's about a year and a half old. It retailed for a little over $500 and I got it from Ike Sound for something like $320 new still sealed with the alpine sticker. Either way, it’s defiantly out of warrantee. It never made any noise with its internal amp. I also find it weird as hell that the sound will show up with only the ground and RCAs connected. Is it possible that they didn’t filter the power rails for whatever reason?

 

It also only does it with the car on if that matters. With the car off everything is perfect.

 

More sillyness.

I jumped the 12v and remote lines on the amp to keep it on and I still have nothing connected to the HU. The car was idling.

Tonight I discovered two things:
- when holding the HU in my hand and grabbing a piece of metal (door frame, grounding wire, etc) the sound will show up. There's nothing connected to the HU aside from me holding it by its chassis and the RCAs
- I unplugged the RCAs from the HU and grounded one of them to the car. The sound came up in that channel. When I grounded both the sound went away.

Could it really be the HU? I'm beginning to think so. Anyone know a good Alpine repair place?

 

What's no longer relevant? You still have noise problems? First, I hope you didn't damage the HU moving things around. It sounds from your posts that you are doing things that are VARY dangers. Bad grounds CAN damage the HU (hope this is not you're problem). NEVER MOVE GROUNDS WITH POWER AND RCAS CONNECTED, NEVER. If you're still having noise problems, do you have a DMM and know how to use it a measure resistance? We need to do some SAFE checking. And we know the make and model of the HU, but what about make model of the amp/s, any x-overs or EQ in the line?

 

The first post was a long winded thing babbling about all kinds of stuff before I found out that it was a ground noise type problem. Basically me going through and trying various things to try to figure out what the problem was.

I'm moving grounds with nothing else connected to the head aside from the RCAs (nothing, no power, no antenna, no speakers, just the RCAs). Simply holding the head in my hand with only the RCAs connected and the amp on and then grabbing a piece of metal will create the sound (that’s how I found this out in the first place quite by accident). Grounding the HU chassis to metal will also create the sound again with nothing connected to it. Again, the sound only happens with the car running.

The head is an Alpine CDA-9833. It’s a little over a year and a half old. This is the amp. here is a link to the component set. Those are the only crossovers I have wired in. There’s nothing else in line. Incidentally, I tried connecting a mp3 player to the same RCA set with the car running. The sound wasn’t present, which means it’s either the head or somewhere in the car’s electrical system. I think it’s pretty safe to rule out the amp/crossovers/RCAs. I’ve also tried two different RCA sets to no avail.

Power/remote run down the driver’s side, RCAs ran down the passenger’s until I tried the other set and now they run down the middle of the car. All the 4 speaker wires run down the passenger’s side.

To answer your question, yes I have a DMM and I know how to measure resistance. Just tell me where to check and I’ll do it.

 

Start by measuring the resistance from the chassis of the HU (any metal on the outside of the unit) to the RCA ground (outside conductor) of the HUs RCA outputs. This should be vary low (less then 5 ohms). Also, check the resistance from the ground wire in the harness to both the chassis and the RCA ground. If all looks good there, check back by the amp. With the HU plugged in, BUT WITH THE POWER OFF, check the resistance from the power ground terminal on the amp to the RCA ground on the cable (with the RCAs unplugged from the amp). That last one make any sense? Post back with what you find.

 

You may have a bad ground elsewhere too, like your engine strap maybe, and your excellent ground through the headunit is being used by whatever the problem is. I would try a couple things, if you haven't already. Replace the ground strap on the back of the engine with good 4 gauge cable, and add a ground (also 4ga) from the negative battery terminal to the car's frame. Let us know what happens.

 

I totally forgot about that! Could be the cause as well.

 

That's 2/3 of the big 3 (negative to chassis, engine to chassis, and positive to alternator out). I just did the grounds with some 2 gauge about a half hour ago by running a cable from the chassis by the radiator to the negative post on the battery to the alternator bracket (one continuous piece of wire that goes through some weird battery terminal clamp thing that I found). I didn’t do the positive to alternator out yet because I didn’t have a small enough ring to clear the valve cover. I also didn’t want to have to dig behind the engine to replace the ground strap because I’ve heard it’s a major pita. Besides, the 2 gauge from the bracket to battery/chassis should suffice.

I no longer hear the coil firing but I can still hear the alternator. If I leave one RCA plugged into the HU and ground the other the noise goes away (again with the HU off and only ground/RCAs connected). My mechanic (I did the grounds at the shop I used to work at) swears that it’s the fiberglass hood. He says that it’s a common problem with vettes and boats and that they use a capacitor connected to the alternator and another connected to the blower motor (heat/ac) to cut down on RF. Anyone have any comments on this? Jim? I know you have a vette.

NEEDAZ: I will do that tonight when I get home from work and will post the results.

 

The coil-in-cap distributors did get a noise supression capacitor...I don't know if the remotely-mounted coils got one.

 

I will say this about the grounds: those suckers really do help. I stayed at 13 volt or higher on the dash gauge when I was driving around today and we all know how accurate that thing is. Before I would cruise around 13 and idle at 11-12.

NEEDAZ: HU case to RCA ground was less than 1 ohm, ground in the harness to the HU chassis was .5 m ohm, and ground in the harness to the RCA ground was .5 ohms. This is what I understood from your last instruction was to connect the ground to the HU and plug the RCAs into the HU, then check the ground between the RCA ground on the cables and the ground on the amp (with the cables unplugged from the amp). I read something like .1-.3 ohms. The reading would flux, starting pretty high when first connected (over 30 ohms) then it would drop down to the .1-.3 ohm range.

While I was back at the amp and the RCAs were unplugged I checked RCA ground on amp (aka the plug that the RCA plugs into) to the ground terminal on the amp and couldn’t get a reading. I switched the DMM over to open/closed and found it to be open. It was also open for the set of RCA outputs (for daisy chaining amps). Should the RCA ground to the actual ground on the amp be open? I’m not sure how much this matters given that the mp3 player played fine, but it’s somewhat weird to me.

My mechanic was talking about a capacitor wired to the alternator and the blower (pretty much anything with bushings) to reduce the RF they generate when active. He says the reason vettes would have them is because a fiberglass hood won't shield like a metal hood will. I'm not sure how accurate this is; that's why I asked the vette guys (and the boat guys).

I don't hear the coil anymore, just the alternator. I have a remote coil, but since I can’t hear it anymore I’m not going to worry about it.

 

Dang it, I was really looking forward to blaming Alpine for this one. Don’t worry about the RCA grounds on the amp, there AC coupled. I don’t go into that on my rants on grounding because it just leads to more complicated question with long answers. But in short, as you start getting variations in supply current to the amp, and the voltage difference between the power ground and RCA ground become excessive (starts looking like audio between the grounds) the impedance between the two grounds drops dramatically. It takes to long and to much math to go much farther then that without getting confused.
You will often see them use caps. in vets and boats as noise filters, but not quite because of the shielding provided by the metal body parts, but more for the extra grounding by the metal body parts. Try tracking a real hard ground problem down in a vet and you’ll see what I mean (Had to do this yet Jim?). Most of your body panels are still metal so I don’t think just you’re hood is the problem. But we shouldn’t rule out RFI just yet and some filter caps may help, but lets see what we can do before going down that road.
Is there any difference in the noise between the radio and CDs?

And for giggles, see what the resistance is for the ground in the HU harness to the battery ground and to the block. Disconnect the battery ground cable and measure right from the cable just in case. You will probably need to use some scrap wire to extend the meter leads out under the hood.

 

I was actually looking forward to blaming Alpine as well because at least then I would know what's wrong. As for the noise, it turns up regardless of whether or not the HU is on, let alone powered. All I need connected for it to make the noise are two things: a ground to some point on the chassis (be it the factory ground wire or any other point) and the RCAs hooked up with the car running and the amp on (jumping the remote and 12v+). With the HU powered up, it doesn’t matter if it’s on aux in, playing a cd, or tuned to a radio station.

I will check HU harness to battery resistance, but it’s probably pretty low because of the brand new 2 gauge running between the engine, battery, and chassis. It didn’t make any difference earlier when I ran a ground straight from the battery to the HU earlier.

I’m going to go outside and play with a few things. Will post my findings. Keep the idea’s coming because I’m defiantly pretty stumped.

 

So if you just have the amp on (HU off) it makes the noise? What if you unplug the RCAs from the HU and have the amp on? That would certainly have me leaning to RFI.

 

I tried that just now without reading your post. Amp on with nothing connected it's quiet. The instant I connect a RCA to one of its inputs that channel picks up coil noise. The noise goes away completely if I ground the other end (outer ring and the pin in the middle) to the amp's ground The noise stays if only the outer ring or the pin is grounded; both have to be grounded out for it to go away. The noise turns into alternator whine if the RCAs are grounded to any point other than the grounding terminal on the amp (even where the 2' long section of 4 gauge meets the car's chassis). That would explain why grounding the HU made alternator whine with the RCAs plugged into it.

It doesn't matter where the RCA cable is run. As long as it's connected to the amp there's coil noise. I even tried running it right out the hatch and away from the car. It didn't impact the volume of coil noise at all.

I tried another set or RCAs to no avail. Think the amp might have issues? I’ve got no idea what to do next.

 

This is from another forum I posted my problem on:

By shier logic alone, that should get rid of the alternator whine, but I'm not sure that it will get rid of the coil noise because that's getting induced into the RCAs. EDIT: this product isn't available from circuit city (or they don't list it on their website) and the manufacturer's website is currently down for reconstruction

Another idea goes back to the capacitor theory. "To make matters worse, the alternator produces small pulses which aren't completely filtered out by the battery and/or capacitors. These pulses create noise that varies with engine (and therefore alternator) speed." The capacitor would be there to smooth out that signal into a more steady stream.

Thoughts/comments on either the isolator or the capacitor? What about the induced coil noise that I still have (it's just not as loud)?

I will be doing the final stage of the big 3 (running heavier gauge wire between the alternator and battery positive) at some point tomorrow to see if it helps at all.

 

Ground loop isolators suck. They filter the problem instead of eliminate it. They also ruin your stereo imaging.

At this point I think your next step is to borrow a friend's amp that's known to function properly, and see what happens with that amp. LIkewise, put yours into his car and see what happens.

 

I had the feeling someone was going to post that. Good to know though.

I also thought about it some and it's somewhat hard to see a loop forming considering how the rca grounds on the amp are not grounded to the chassis. That right there should break the loop. It’s probably more along the lines of feedback or something like that.

I have a little more info on the mp3 player: I swapped my the car style twisted pair that I had on the amp for the minijack to RCA cable I was using earlier and the induction noise was still present. It went away completely when I plugged the minijack into the mp3 player's headphone port I swapped back to the RCAs and plugged them into the HU (with the HU completely unconnected from everything) and the noise stayed the same.

We will see what happens first: my NINe.4 gets here or one of my friends comes home from college for a day.

 

Shouldn't need an isolator.
You don't have the chassis of the amp grounded/screwed right to something metal do you?
Every thing plugged in, the CD player on, volume down on the HU, and if you touch the HU chassis you get the noise?

 

I haven't tried this with the HU powered up in forever I've always just done it with the power off. I guess I could try it. It will have to wait for tonight because I need to resolder my harness and I'm running out of time with class and work coming up soon

The amp is on top of the hump. I have screws going through the carpet into a piece of MDF I stuck behind the carpet since I've read all the posts about drilling into the gas tank. The screws shouldn't be making metal contact. I can lift the amp up some because it's really just attached to the carpet so I don't think it is.

As for the amp's actual ground cable, it's a 2 foot long piece of 4 gauge that's crimped to a ring connector that's bolted to the car's frame.

 

I've been talking to Jim on IM. Here's more or less what we've found: grounding the pin to the ring on each rca cable makes the noise go away. According to Jim this means that the amp has an internal ground loop.

Again, the amp doesn't make any noise without the RCAs plugged into it, it makes noise with the RCAs plugged into it, and now I can eliminate the noise by grounding the pin and ring on each channel individually with a piece of wire.

 

Another post with yet more info. I wired up the HU again so that everything that I will be using in the long run is connected (dimmer, antenna, 12v, ignition, ground) with the exception of the remote wire. I decided to continue using my jumper wire on the amp in place of the remote.

I have a few interesting things to report: first, the RCAs are defiantly picking up RF or something else along those lines. When I turned the key to on before the HU had a chance to turn on I could hear my car's fans start to spin (they’re hardwired to the ignition). After the car started I could hear the alternator for about 5 seconds. After the HU had a chance to turn on (takes about 5 seconds for it to 'boot') the alternator sound went away completely along with a nice pop from the current spike of the HU turning on. The fan/alternator sound probably wouldn't be that big of a deal if I was running the remote because the delays wouldn't let me hear the fans/alternator. I just thought I would post for reference. It’s really not a big deal at all because with the HU off the remote will turn the amp off so it won’t pick up any of the noise.

I still heard the ignition coil firing, but if that’s really the amp like Jim is suggesting it should be fixed when my next amp gets here. In the mean time he’s having me try a few things involving 10k resistors.

As always, comments and other ideas are welcome.

Also, don’t worry about me wrecking my Quarts with all these sounds/pops. I hooked up the stock 6x9’s so they can take the beating

 

If you're getting the pops, clicks, etc, then I still think you've got some sort of issue with the amp power supply filter or you've got an imbalance between the signal ground plane and the power supply ground plane within the amp.

 

I'm not arguing with you at all. Coil noise is there but the alternator whine is accounted for. The pop when the HU powered up with the amp hardwired on was also accounted for - the amp would normally be powering up when that spike went out from the HU so I wouldn’t have heard it if the remote was connected.

As for the resistors, tonight was a busy night at work and I didn't get out until 11 - well after radio shack closes. Hopefully I will have a chance to make it there tomorrow so I can play around with the amp.

 

I finally had a chance to run to radio shack today. After I got home I sat in the back seat of my car trying out different combinations of 10k resistors between the RCA ground and the pin. At every point I checked the resistors against a piece of wire to make sure that the sound was completely gone. At first I tried two and three resistors in series but there was no noticeable effect so I switched to parallel. 5 10k resistors in parallel did the trick (2k total resistance)

Now then, how do I wire up a clump of resistors (or even a single 2k resistor) with the RCAs hooked to the HU to test it?

 

Don't. I'm not sure if your head unit will like such a low impedance on its output. I was hoping to see your noise go away with at least 10k or higher resistance.

If you can get ahold of a tech from whoever makes your head unit and ask them what the minimum amp input impedance that head unit can handle, maybe it'll be ok. Needaz may be able to provide some insight too. I've never experimented with this sort of configuration. I would have felt ok if it was 10k or higher, but 2k is pretty low.

 

Sounds like a plan. I'm still slightly confused on the internal ground problem on the amp. Since there's no noise with the RCAs unplugged and noise with them plugged in that makes me think there’s some sort of isolator problem or something else along those lines. Logic tells me that the cables are picking up coil noise, but I doubt that’s the case if I can have the amp mounted to the hump and then run the RCAs straight out the hatch and away from the car.

Confusion ensues in my head :? Either way it seems to be the amp's fault.

I'm not sure I want to worry about contacting Alpine about the impedance because I'm going to have the new amp here fairly soon. Maybe Needaz will have some info like you said. Regardless, new amp (NINe.2x) ships monday/tuesday . Hopefully that will prove to be the problem.

 

The HU should be fine with the 2K load as long as the amp has a good high input impedance (and the Infinity will). The output lever will drop some and it is hard to say how much, may be just noticeable, may drastic.
About the amp, the amps RCA ground is AC coupled to the power ground. They just use a cap from the RCA ground to the power ground. This means that there is a high DC resistance but low AC impedance. So in theory audible noise on the RCA ground should pass through the cap to ground and not get into the pre-amp. If the connection from the RCA ground to this cap, or the connection from the cap to the power ground is bad, this will not happen. I’ve seen this happen on a Kenwood amp. But that one had some other things going on to so the symptoms where a little different, can’t really compare the two.
Jim, what do you think about a 1000pF-100pF cap in parallel with a 1K resistor from the RCA ground to the power ground? This seems to be common practice to couple the RCA ground to the power ground. If there is an open some where in this line, this should do the trick.
The other rub may be that some amps use noise filters (the think of a transformer on it side kind) between the RCA ground and RCA signal. If this is open in the amp (or bad solder connection) on the ground side of things that would also cause this symptom. Is that what you’re thinking Jim? Because of the cap there’s no real way to check this without taking the amp apart. You could ring it, but I think the input buffer (OP amp) would abject to that with some smoke.
Your meter have a cap check function through the leads Gummie?

 

That's a good question and I can't give you a good answer. This is the multimeter. It's not that high end so I doubt that it has the function, but it might.

I will wait for Jim’s reply on the resistor/cap question and then run over to radio shack again and pick up some bread board so that I won’t have to hack anything to pieces. As for opening up the amp, I don’t have a problem doing that. I have already been inside it once to replace the PSU controller chip that I managed to fry when the amp’s ground vibrated loose from the car’s chassis (now there’s a lock washer there and I’m using a crush bolt – don’t know the real name).

If you want me to pull apart to poke around some I can.

 

We're getting out of my area of experience here. The few amp designs that I've looked at recently all used the "star grounding" principle and had no AC coupling. I'm going to stay out of that part of the conversation until I can learn more about it.

 

I'm not even sure that the amp uses an AC circut thinger. To make matters easier on us all I think I'm going to pull apart the amp again tonight or tomorrow. Ill report my findings.

 

Jim, Those designs by a company that starts with an A? I could drop you some schematics if you’d like something to study.
Gummie, I don’t have service info on hand for those models so I can’t really say how there doing things. Just going off of how most do it most of the time. Unless you find an open trace just by looking, it’s going to take so knowledge to get through that thing with out the schematic. Really, I would just cross my fingers until the nine.1 comes in.

 

Needaz, the stuff I was looking at was schematics for class A op-amp home amplifiers, but I'd love to stare at some schematics if you've got them!

 

True that it is a pretty big stab in the dark, but I've got nothing better to do when I'm out of class and if it does turn out to be something stupid then why not fix it? The vulcan death grip the first set of RCAs had on the RCA connectors on the amp might have had something to do with it too.

Incidentally, I have a NINe.2x coming to me. I won’t be ordering a NINe.1 for a little while because there’s no sense in buying it until I have my next box built and my new subs in it. Not that it really matters, just thought I would throw it out there

 

Pulled the amp apart and couldn't find anything visually wrong (gasp). Put amp back together and reinstalled.

I'm just going to wire it back up to my subs and wait for my NINe.2x to get here. I will post again once it's here to say whether or not the infinity was the problem.

Thanks all for the help up to this point

 

I recently repaired a 7 year old amp which would sometimes shut off a bizarre times, stay that way for anywhere from a few seconds to 10 minutes and then mysteriously turn back on. What it was in my case was four resistors with bad solder joints. Looked like it probably made it out of the factory OK. I know I didn;t have problems with it until about the 7th year. I've heard of some resistors with a dirty outer lead surface which would not allow solder to adhere very well. With time, they get more & more loose. I removed the resistors and used a razor to scrape the leads clean (solder wouldn't stick), resoldered them & the problem's fixed.

I'd suggest looking for small breaks where the solder meets the component leads. Probably a resistor or cap is to blame. Since both channels are having the same problem, it probably is a something such as this. Actually makes it easier to track down.

 

I've had similar problems with GM's piece of crap digital dash that was in the 90s S10s. I took mine apart and it looked fine, but I re-soldered every single ground pin I could find. I reinstalled it and it worked much better... for a while. A bad solder joint can be hard to diagnose, but it may be worthwhile to resolder every pin on the ground plane in both the power and signal side of the amp.

 

That's the problem, I'm not 100% sure where every pin is on the ground plane. There was one random wire that ran from the board and it was bolted to the heatsink, but that couldn't have been a ground because it wouldn't have gone anywhere. Maybe it was to ground the HS?

Anyway, the NINe.2x shipped. It will be here Monday. If the sound goes away with it installed then great, the infinity was the problem. At that point I will do one of three things: say screw it and reinstall the infinity on the subs and not worry about it because the subs can’t play the noise anyway, buy some breadboard and make a filter consisting of a 2k resistor, or get really bored and try to trace out/re-solder everything.

 

I've seen those, too. I never looked long enough to see where it went. It's probably someone's idea of an RF shield. Not a really good one since most heat sinks are aluminum, but...whatever...

 

Every amp I've ever opened up (or looked at the schematic for) has grounded the chassis. It's standard practice in almost any electronic device.

 

Chassis ground, they all have it (but some use different ground potential). Poor RFI protection because it’s aluminum? Small RF vaults are made of mostly cast aluminum. And the doors on large RF vaults I've seen are aluminum. Be fore you just use a 2K resistor to load things down, I’d try a small cap and large resistor from RCA ground (signal ground) to the power ground. If that works it should have less of a negative affect on the input signal from loading.


BTW Jim, I didn’t get out of the second job until after 11:00, I’ll try to mail them tonight, if I get home before I fall asleep.

 

No rush. I've got more than enough Switched Ethernet documentation to fish through at work to keep me busy long into the night for the next few days anyway.

 

ever get your noise problem worked out? i've always had a small bit of alternator whine, tried a bunch of different grounding spots in the back and up front and just can't eliminate it completely, so im just going to run another 1/0 gauge from the negative terminal back to my amps and split it into 4 gauge wires there. if the bad ground is up front like i think it is though, i might still have some deck noise to deal with.

i know its the amp grounds because i hooked up a cd player with a headphone jack to rca converter and it made the exact same noise. i figure it can't hurt anyway with the monster amp thats going to arrive tomorrow

 

Sorry, but I never even realized that you posted wondering if I ever got it sorted out. The answer is no. I ended up pinning the blame on the amp and I'm still not sure if that's the problem.

I don't have any alternator whine at all, just a faint clicking that sounds exactly like ignition noise. It just doesn't make any sense because I can run the RCAs wherever I want (including out the hatch and away from the car) and the noise stays.

I got my NINe.2x today. Dead sexy amp. Too bad it's 12:30 in the morning, cold, and raining otherwise I would hook it up now. Maybe if it wasn’t raining... I'm going to try to get it installed tomorrow between classes (yay for living 5 miles away from school). I will post a follow up as to whether or not that cured the ignition noise sound.

 

got my crossfire hooked up, just to test it out, and it slams those 12's hard. i've got it turned up a little over halfway, and it rocks. i havent even ran the ground from the battery to the back yet, should have all the extra wiring and terminals i bought for that in a couple of days. i have no highs, because i had to use the power and ground for my diamond for the second power supply on the crossfire, but i think i'll be alright for a couple days lmao

 

Final update

I finally got everything installed. First let me say that ANL fuses are freaking huge as are their inline holders. Even with only a 200 amp (haha, only ) rating the fuse looks like a piece of sheet metal wrapped in some plastic.

That said, everything works/sounds great. I'm not going to bother wiring the infinity up to the comps again to see if it's still making noise; I will just be happy that its above the lpf cutoff point so I don’t hear it even if it is still there. The NINe.2x is a beast. I’ve only got the gain up about a quarter of the way and the subs/infinity are having a hard time keeping up.

Unfortunately, I changed about 10 other things while I installed the new amp so I can’t say for certain that the Infinity was the problem (unless I was to hook it to the comps again but as I said before I’m too lazy and don’t really care). The car is now fully wired in two gauge (alternator to battery +, battery – to chassis, battery – to engine. For the amps I have a single two gauge wire going to a fused distro block with four gauge running to the amps. Ground is the same as power except it’s unfused. I’m also running KnuKonceptz Krystal Kable for my RCAs now.