I've got a noise problem in my IROC that's really starting to drive me nuts.

When I load a cd into the cd player, I hear beeps/pulses through my speakers. I think this is related to some sort of switching noise that's getting into the signal path. I get the same sort of noises/pulses when pushing the forward or back buttons. The noise floor is also excessively high with cds.

Now here's where it gets wierd. With the radio, the noise floor is super low.

Here's where it gets wierder. I swapped head units and it still does it.

So, since then, I've run new RCAs down the center of the car, regrounded the head unit to the ground block where the amps are connected, grounded the chassis of the head unit, and even played musical amplifiers to see if an amp was at at fault.

Absolutely nothing impacts the problem at all.

All I have left to do is try a new power line to the head unit, but since I'm running that direct from the battery already, I'm not real sure that's going to help.

Needaz, if you're reading this, do you have any suggestions for where to look next to cure this?

 

sounds like you have covered everything.. grounds would have been my first guess....

when you "swapped head units " did you swap it for another unit of the same make/model? if so it my just be a feture or common error with that unit. if not then you got me... my pioneer dehp650 in my 86 has started to do that too as it gets older you can actualy hear the motor moving as it skips tracks and loads/ejects discs through the speakers

 

How high up does the volume need to be to hear the noises? I could hear all the head movements and CD loads in my old Sony ES at almost full volume. And clicks when adj the volume.

 

One head unit is a JVC SH909, and the other is the Eclipse that I pulled out of my Corvette. Soon I'll be pulling the Kenwood XXV-01D out of the corvette to try it too.

Justin, this is at low-ish volume. I already backed off a MILE on my gains to help make the noise floor tolerable, which might be eggagerating the cd pulses/beeps because I do have to have the head unit turned up farther.

But... if I recall, these noises are independant of the volume, so the noise must be getting into the signal after the pre-amp stage.

As for the noise floor, it's so bad that when I turn the volume control from "0" to "1", I can hear the static noise. From "1" all the way to full volume (78 or 80 I think? Either way, the arbitrary number isn't important) the noise level is constant.

 

Dambit man, figures you get the really whacked out stuff. Had to do so thinking on this one. The both decks thing is throwing me. I can come up with several things internal with the deck that could cause this, but that would mean both decks would have to have similar problems.
Tuner is good, CD is bad on both decks? Just throwing some thoughts out there as brain food. The EVTC IC does have different gains for different inputs, I suppose the output impedance could be changing with different sources. But you can more or less rule out impedance problems because that JVC uses line drivers after the EVCT IC, if impedance was the problem, I would think these would have the effect of making any kind of impedance problem the same for all the sources. The HUs sound good in other cars? And you used different amps and it was still there? Did you try another car amp? Back to the decks, zero bit muting problems? The DSP should be muting between tracks. That one’s out there. I think the microprocessor should be muting things between tracks too. For the JCV, muting is handle by taking the signal to ground through a 2SD1048 after a 1K resistor. You could try muting the RCA outs yourself to see what happens. Some scrap cable, cut the insulation back and short them to see if your still getting noise between tracks? We both know what should happen, and I can’t see it not happening. But what the hay, at this point I’m just brain storming. Back to think some more....

 

Did it start all at once or over time? Did you change anything at all when, or even just a little bit before the noise started? You're certain that the radios DON'T make the noise in other cars, even under the same situation where the HUs volume is adjusted higher then 'normal'?

 

I'm not sure if it's something that just started, or if it somehow took me this long to notice it. I'd like to think that I would have heard it before if it was there.

The first time I really remember hearing it was when I got the JVC back from repair this spring. I put it in and immediately noticed the high noise floor. I had assumed that they screwed up something during the repair until I swapped in the eclipse and experienced the same problems.

The eclipse was in my Corvette for a very long time and I never noticed the noise in my corvette, but to be fair, the eclipse amp that was in that car had major gain problems that prevented me from being able to get full output from that amp, so it may have masked the problem. When I work up the motivation, I'll throw a 3rd head unit into the IROC and see what it sounds like. I really don't remember having this noise when I had my Alpine in there, right before I put the JVC back in.

 

I'm wondering if you are getting some ignition interference. I had a similar problem with my setup in my Taurus but I wasn't hearing internal sounds from a radio, I was hearing pulses from the ignition. I found a relay box that was on the firewall right behind the radio in the dash. I moved some wires like you did with the ground and power but nothing changed. I put a cheap audiopipe noise filter at the head unit to the pre outs and it disappeared. Strange because the preouts don't affect my mids only my subs. but none the less it is gone.

 

try this:
ground the outer ring of your RCAs to your head unit. i had an oddball noise issue with my amp the other day and this fixed it.

 

The outer ring should be grounded to the HU chassis. If yours wasn't then that would explain why you were having a problem

 

My US Amps said in bold in the instructions to test with a VOM and ensure that the chassis ground and the outer ring of the RCA are common. Otherwise it said to solder a ground to the RCA. These are the only amps I have ever had that specifically instructed to ensure this.

I have had a similar noise problem in the past when my amp shorted internally and grounded through the RCA, frying my crossover. Sounds like Jim already switched everything, though. What is even stranger is the fact that the noise is different on different sources.

Do the speakers whine with the radio off? I know it sounds stupid, but a friend of mine put components in his BMW and stuffed his crossover on the driver side in the dash in a cluster of wires (I have never seen as many underdash wires in my life as in that car). He called me and told me that his driver side speaker whined without even haven an amplifier connected. I thought this was impossible and was prepared to call him on one of his many stories. I went over to his place and looked and listened and sure enough, somehow, apparently the coils in the crossover were picking up a signal in that cluster of wires and playing a ,loud, annoying whine with no amplifier even in the car.

 

Everything is dead quiet with the car off. Right now my crossovers are sitting on the back seat, far away from anything that can induce noise.

I haven't tried any power filters yet, but I may soon. I don't want a filter in my signal path though, so if a power line filter doesn't help, I'll have to go back to finding the root of the problem.

 

That doesn't make much sense to me because you're not hearing ignition noise or anything else along those lines. All your noises originate at the HU (noises when you push the buttons, etc) so it should happen regardless of whether or not the car is on. I want to say that you have a dirty power/ground but you’re running power straight from the battery and you’ve already beefed up the ground

 

none of it makes sense to me. Common sense says that this is a head unit problem, but what in the hell are the odds of having 2 head units with the exact same problem?

 

Hey Jim, I have the same problem, and discovered it was not the head Unit but the actual amp itself.

Does this noise come through ALL of your speakers including the sub?

I have an older Rockford Punch 200ix that does this (what is happening to you) and for some reason about a year after I bought the amp it started to make a funky noise everytime I changed tracks on the HU, or when I power the unit on or off when in CD mode. The radio is all good, just like you said yours is.

I put a RCA noise filter in line before the amp and it cured it.

I put the amp in my truck and its doing it again because I forgot the filter in Hawaii.

I would say that if you have just one 4 channel amp driving the highs and they are the only speakers making the noise, to check the amp itself, the RCA inputs especially.

If all of your amps are doing this, well, I have no idea.

-Matt

 

Could it be the power switch in the amp? I noticed last night 1) my driver front speaker has a nasty hum to it i have to find taht is incredibly annoying - and also when i turn the hu on or off, when the remote hits the amps (they have a 2 sec delay to prevent sucking extra juice) that the speakers kinda have a noise that goes through them. Maybe its when the amp turns on, whatever is causing that is jumping/shorting somewhere in the amp? If you have time to kill, wire your speakers direct to the hu to start weeding crap out. That way you'll know if it's the hu or processing after the hu causing the noise. Go from there. Systematically eliminate things in the chain till you find it.

 

I've already eliminated the amp as a possibility unless both amps have the same problem.

 

And the HU by the same logic. I'm still thinking, you got a 4 wire ohm meter?

 

a what?

I've got a cheepie Craftsman DMM, and an analog oscilloscope that my learned-on-a-digital-one *** doesn't know how to work.

 

Power leak? Blown inline fuse? When you change channel, technically the power is gonan dip for that second or 2 you are changing.

 

what?

 

Thats what happens when you browse message boards while giving tech support for a dial up isp. Have you checked for any blown fuses? Like the inline fuse, etc. If the fuse isn't blown fully, and the power has to "jump" from terminal to terminal, it may do that. Doubt it, but i dunno where else to look, and the fuse would remain constant between setups.

 

 

That seems to make sense. If an inline fuse was partially blown, the headunit would not be getting all the juice it needs, and would become noisy when trying to draw power. It's a long-shot (really long), but you never know.

I'm still not sold on your grounds not being the problem. No offense to your craftsmanship, I know what you can do, but I can't shake that it sounds like a grounding problem, probably with the RCA wires or connectors.

Does the noise amplify when you turn up an amp's gain?

 

Good question.
And what, you don't keep a meter around that will measure down to 1 micro (not mili) ohm? I was still thinking grounds on that thought. But all this fuse BS has me thinking. You ran power for the HU right for the battery right? Well, are you using a relay to switch the ACC to the HU off of this power wire? Any other switches in the line? Is that the way you've always had it. Try measuring the resistance from the B+ terminal on the battery right to the HU harness (with ground off of the battery, but I didn't need to say that.).

 

yes, the amplifiers gains effect the noise... so the noise is in the system prior to the preamp stage of the amp.

I've been skeptical of grounds too, which is why I tried new ground locations for the head unit, and even tried running a ground from the head unit chassis.

My power wiring is as follows:

2 AWG from battery to 100 amp breaker. Post breaker, I have 12 or 14 AWG going thrugh a 10 amp fuse and then directly to the head unit. Basically, I tapped off of my amplifier power after the breaker so that when I disconnect power from the battery to work on the car, the stereo's capacitor helps me retain radio presets.

Switched ignition is the factory wire in the dash board.

I can try to jumper out the breaker, and I can replace/bypass the smaller fuse to see if it'll help.

 

Try jumping out the breaker. Had a JVC that had other noise problems once, that had a wire right to the battery and a relay for the Acc. The relay contacts built up some resistance and at higher volumes the amp would go into this strange oscillation. Weird, but not what you got going on.
Just to refresh, Tuner is good, CD has a high noise floor and noise (possibly digital hash) between tracks? And you said that with the engine off/Acc on that everything is dead quite, no noise? That last one is odd too. Dambit.

 

Wrong. The noise is present all the time, including with the engine off. Actually, that's when it's most noticable, because the car exhaust drowns out a lot of the noise when it's running.

 

You have a breaker inline ...crap..that gives me an idea to fix my problem ..thanks. But those breakers .. is it the litlle lever thing that you press a button to disengage, then push it down to re-engage? Maybe a bad contact? Can you clean it? I'd say start by jumping the breaker and see what happens.

 

Jim any updates?

 

Nope. It's too cold out for me to give a sh*t. If we ever get a warmer weekend and I'm not snowmobiling, I'll get back to it.

 

I know the feeling - unfortunately for me this weekend is a good weekend to do it - a friend of mine is a sound nut as i am - so 2 heads tryin to figure this out will be a good thing. Hoping ot have it fixed tomorrow night ... or atleast greatly narrowed donw