Engine whine... engine, or speakers...?

So - Everyone talks about loving the sound of their engines. In my (new to me) 996, all I hear is a constant high pitch whine... I have a feeling it is electrical noise from the ignition feeding into the aftermarket amp (the previous owner put in an aftermarket head unit and amp)... I plan to disconnect the 12v power going to the amp and see if I do indeed get rid of the whine. Any advice on how to filter out ignition noise from the amp? I'm not a "stereo" kind of person, so this is new to me. Also - the amp is a Rockford Fosgate. Thanks... (sorry if it doesn't make sense, I had a 17 hour day in class+office today)

It could be what is known as alternator whine which can happen when the RCA cable from the head unit to Amp is in too close proximity to the Amp power cable. Ideally you want to have those two cables run in separate paths. The issue with the 996 is there is only one grommet in the firewall that you can use to run the RCA and Power into the front trunk. In this situation using an RCA cable that is a highly shielded can help. I used the KnuKonceptz Krystal Kables and routed the Power and RCA wires as far apart as possible...no alternator whine... see this post if you need more details... https://rennlist.com/forums/996-foru...-underway.html

Hi Fly, thanks for the info... As far as I can tell (in my 1 minute of poking around in the frunk) the power cable for the amp is coming straight from the battery's positive terminal (with a blade fuse inline), so it is not coming through the firewall... and therefore I am guessing it is not near the RCA cable - but I could be wrong. I'm posting the best (and only) picture I currently have of the amp... will try to get more pics tomorrow in daylight. From what I see, the left side has 4 RCA cables plugged in, the right side has several speaker wires entering, a + and - power cable, and one more + cable (I'm guessing one is a constant +, one is a switched +). I'm thinking the first step is to get a better head unit... since I detest the current one in there.

Full the fuse to confirm it is coming through the amp/speakers... Assuming it is, it is often caused by poor grounds or low quality/defective RCA cables... It's best to find the source and fix it, but you can also try just throwing in some inexpensive ground noise isolators and see if it fixes the problem. About $15, you'll probably need two if you have a four channel amp.

Changing the head unit probably will not solve the problem if it is a wiring noise issue. I suggest removing the spare tire, the back part of the trunk liner and the (3) battery cover pieces to see exactly how the wiring is being run.

Sailor--I replied to you briefly in my thread. Basically, it sounds like you have a ground loop in your system. Although you can use a noise filter to remove the interference, I would use that as a last resort since it doesn't actually fix the problem. If you used braided Eva cables I seriously doubt if you're picking up any noise from the other cables, even with a long run. Chances are, in your 911, your cable run is very short since I'll bet the amp is in the trunk with the battery. I'll send you a link to a good site that is an excellent reference for resolving ground loop whine.

I had the same problem and it was poor ground on the head unit.

Thanks for all the good info guys! I'l try to poke around in there this weekend if I have a chance. I do plan to replace the head unit ASAP anyway (I don't like the style of the one that's there now, and want one with touch screen, etc). So I'll probably double check all the wiring there (ie, ground for the HU, antenna cable, etc) when I pull the existing HU out. Is it easy to get the trim pieces off the dash to pull the HU?

if I recall correctly, You do not have to remove the trim to pull the radio. You do need these to pull it out though. They act as handles on either side of the radio.

Hi SJG, not sure if I would still need those, as there is now a JCV stereo in there... I need to remove the trim anyway at some point to fix a broken "door lock" button.

Okay--below is the link I was mentioning. ANYTHING you want to know about car audio is on this site--even how to repair amps and head units, etc. If you take the time to go through all 139 chapters, it's like a mini Electrical Engineering degree... :-) http://www.bcae1.com/ Once you go to the site, there will be a sidebar on the right that can scroll. You want to scroll to chapter 95--troubleshooting. Ground loops are down a bit from the top. Anyway, 99% of the time it's due to a bad ground creating differing potentials with the other grounds on the chassis/battery. Also check for your RCA shield ground if you're using RCA cables. It's a VERY easy thing to do on your head unit--just check continuity between your RCA shields and your head unit (turn multimeter to resistance and touch one end to the RCA shield and one to the chassis--it should drop from 1 to zero, or close to zero). It's very easy to fix--wrap wire around the outside of all of the RCA outputs and then connect it to the head unit, itself. Good luck!

The horseshoe and other trim pieces are easily removed however I would recommend use of a car audio trim removal kit in order to prevent scratches.

If your car came with a factory amp in the frunk and the original connector that plugged into the factory amp is unplugged that could be your problem. The ground on the connector should be connected to ground. The "floating" end of that ground wire can pick up noise on the power wire and feed it into the head unit. No, I don't know which pin is ground.

It's not the 'polarity' of the grounds... I'm sure they are hooked up pos to pos and neg to neg or you wouldn't be getting anything at all. It's the *quality* of the grounds... Connected to a bolt that has no paint or other insulating crap on it, ground wires crimped or soldered well, ground wires are as short as possible and of a large enough wire gauge, the ground bolt itself has a good conductivity to battery ground, etc.

pfbz... actually, if you wire up a speaker with reverse polarity you will get sound. However, oftentimes the sound lacks bass for one very simple reason. When you hook up a speaker with the pos to neg and vice-versa, you have set the speaker to be out of phase by 180 degrees. With the longer wavelength of bass, these sounds can actually cancel out the bass from other speakers. It's the same principal as having a phase adjustment dial and/or switch on home subwoofers. But speakers hooked up backwards *will* play, so you have to be careful (the only way you won't get sound with wires hooked to a speaker is if one of the wires is loose, has become disconnected, etc). As for grounds, the only grounds that matter as far as speaker noise go are the actual equipment grounds. These are the head unit, amp(s) and any other electrical device that is between your music source and the speakers. The speakers have no other place for their negative terminal to connect but to the amplifier. pfbz... I just realized that you likely weren't talking about the speaker grounds (using "polarity" threw me off). And hooking up power wires backwards could very well end up with worse than no sound! :-) As you stated, the quality of the grounds is paramount. NEVER use a factory ground. Always create a new one, and make sure your ground wire is substantial enough to carry the load. Also--keep the ground as short as possible. Check the ground cab;e the guy installed for your new amp. It should be as big as the power cable going to the amp. If it is, check the location that he grounded it to. It needs to be a substantial piece of metal (ie, not a body panel). It also needs to be free from dirt, paint, grease, etc. I always use a grinder to get fresh contact with the chassis of the car, and once the ground is made I cover it with a sealant to prevent corrosion.

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Yes... out of phase speakers. I thought you were talking about checking the 'polarity' of your 12V power and grounds, since that's what we were initially talking about. Out of phase speakers might cause some issues, but definitely not alternator whine! ---- And I just noticed that you realized what I was talking about and mentioned it at the end of your post! All good!