ormy

I've just replaced the Blaupunkt Toronto cassette with a Alpine CD/radio. After much cursing because of all the DIN/Iso adapters I've had to find to avoid cutting cables, I've got it working. The head unit feeds an amplifier under the seat. The cable feeding the amp is shielded according to the supplier.

Sounds crystal clear when the engine is not running, but when I get low level static when the engine is running. This happens both on the radio or if I play a cd.

Anybody know what's causing this or how to fix it?

doug751

Mine did the same thing. I bypassed the amp and it went away. I removed amp and all is well.

deep_uv

Arcing from your ignition system can cause this as well although it sounds like you didn't have the problem before the stereo install. Might be worth your while to check your engine bay for any arcing by idling in the dark. I had a loose plug wire that caused this same effect.

Regards,

Steve

adamfogerty

As mentioned above if you didn't have the noise on the old stereo, logic suggests you changed something when you hooked up the new one...maybe by accident? Have you checked, double-checked and tripple checked your work?

I'm trying to troubleshoot a 'popping' noise from my stereo at the moment. I found this on another forum, unfortunately I don't have the original link any more so can't credit the source:

The Ten Commandments:

I. The best cure is prevention. I can't overemphasize this point. If you've ever spent an entire weekend tearing an installation apart in order to eliminate some noise, you know what I mean. Take the time to sketch the system out before you begin the install. This graphic representation of the installation will help you to avoid introducing ground loops and will serve as a road map for eliminating noise if it is present.

II. Don't introduce ground loops. Ground loops are created whenever an audio ground is established at more than one location. Theoretically, the only place the audio ground should be connected to the chassis ground is at the source unit. In my experience, I've found that in systems that have noise problems, a ground loop is the culprit nine times out of ten.

III. Never run signal wires alongside power cables. This is especially true in installations where high powered amplifiers are used. Large amplifiers are capable of drawing large currents. These currents vary with the musical demand of the program material as does the electromagnetic field surrounding the power cable. The more current that flows through the wire, the bigger this field becomes. If audio cables are located in close proximity to this fluctuating electromagnetic field, noise could be induced into the system.

IV. Always use 100% shielded audio cable. This will insure maximum protection against induced noises by power cables and other sources of electromagnetic interference. Good audio cables are not cheap. If you prefer to make your own cables, I would recommend using a wire with a foil shield surrounded by a drain wire.

V. Never use the ground wire in the vehicle's OEM radio harness. This wire usually makes a very poor ground due to it's length, small wire gauge, close proximity to other power wires, and unknown termination point. Instead, ground the source unit directly to the chassis or firewall.

VI. Make sure the amplifiers have a good audio ground reference. In order for the amps to function properly, the audio ground must be referenced to chassis ground at the source unit. If it is not, the amplifier could oscillate. To check for a good ground reference, take a volt-ohm meter (VOM) and measure the resistance between the chassis of the radio and the shield of the RCA line level outputs of the radio. This reading should indicate a direct short. If this is not the case, grounding the shield of the RCA line level outputs to the chassis of the radio will probably be necessary.

VII. Keep amplifier power ground wires as short as possible. The longer a wire, the more resistance it has. When a current flows through a resistance, a voltage drop is produced. Because of this, the ground reference at the amplifier's circuit board is no longer the same as that at the chassis of the vehicle. This ground potential differential can lead to noise and improper operation of the amp.

VIII. Don't connect all of your amplifier ground wires under one bolt. Contrary to belief, this is not required if the rest of the system is installed properly. If you do connect more than one power ground wire under a single bolt, you run the risk of amplifier ground modulation. This is caused by the current demands of, for example a woofer amp, modulating the power ground wire of a tweeter amp. This results in a squeaking noise that can be heard over the tweeters whenever bass notes hit.

IX. Make sure all levels are set correctly. Level setting is a critical part of the installation process. If done properly, maximum system signal to noise ratio can be obtained. Keep in mind that you want to drive the audio cables that feed the amps in the rear of the car as hard as possible. To do this, reduce the gain of the amplifiers to minimum. Turn up the volume on the source unit to 80% of maximum. Now adjust the input sensitivity of the amplifiers upward until the maximum intended loudness is obtained.

X. Noise filters can only reduce noise, not eliminate it. A noise filter is just that, a filter. And like any other filter (crossover network, etc.), it works by modification, not elimination. Some installers rely on filters heavily. In some instances a filter may prove necessary, but I believe that if the system is installed properly, a filter is usually not required.

Also have a read of:

http://www.ofsoundmind.com/OSM2/tech...noisecheck.htm

http://www.teamrocs.com/technical/pages/noise.htm

http://www.crutchfield.com/S-PdLQbt8...ech/kb348.html

Hope it helps and good luck,

Adam

ormy

I'm not sure if the problem existed before the new system, as the old Blaupunkt had terrible radio reception and I never tried any cassettes.

Thanks for the tips - I can see I've got quite a bit to work on!

MisterRisky

Adam, that's really great info. All I can add is a hardy "Amen" to the parts about grounding and ground loops. While I have only done radio installs a few times, the problems with noise have always involved the ground.

ducnine

Does your audio systems sound real good?

Mine sounds like Butt!! One of the previous owners put a JVC head unit in and it looks like the stock speakers are still in place...but it really sounds horrible. I can barely hear anything very clearly, and there is no Bass.

Did 964's have good sounding systems from the factory and when replaced with aftermarket stuff, does it actually sound good...except for the minor issues you guys are having?

MisterRisky

If you have factory speakers it is going to not sound very good. Even if the speakers were good in 1990, 17 years of heating/cooling/vibration is hard on speakers. Modern head units give many more options for tuning the music (built in equalizers, better power, etc). You will be surprised by how much better the sound will be with modern speakers and a modern head unit. Of course with the Targa top off it's going to sound like wind noise!

I just put Polk Audio 6.5" components and 6.5" coaxial speakers in my 91 Targa. I had to modify the baskets inside my doors to take the 6.5" speakers, but the holes lined up really nice. The back took a little fabrication work, but mostly dremmel tool stuff. The result is good but I HATE the grills they came with. Here's what I put up front: http://www.polkaudio.com/caraudio/products/db6501/ They have really terrible ricer looking grills, however. I ordered some replacement grills from Parts Express: http://www.partsexpress.com/pe/showd...number=260-422 I bought my Polk speakers from Crutchfield, who I am really loyal to. I love buying stuff from Crutchfield as I have it on my porch the next day since they are located less than 100 miles from my house.

I have an after-market head unit that one of the POs put in. It does not go through the factory amp under the passenger seat. I plan on replacing my head unit in the near future as it does not even have a bass/treb adjustment. Its a Blau from about 1995.

ormy

I've had a mixed result. When I bought my C2, the sound was awful and the head unit etc. were factory supplied (I think). I chose to change the head unit initially because I wanted to play cd's and chose an Alpine head unit. I thought the speakers would be next, but I hadn't started looking around for them yet.

Once the head unit was installed I was pleasantly surprised by the sound through the front speakers. I have no problem with bass. The rear speakers (tiny little things) are another matter - they sound terrible and will have to go.

Jeremy Pinsly

I had a similar problem when my audio system was installed. Low level static with the new amp. Put in a different amp and the static went away. Problem might not be in the wiring, but in the amp itself.

ormy

I discovered something strange today - the static is only there when the engine is running and the headlights are off. I switched on the headlights today and to my surprise the static disappeared

My first thought was "perhaps a dodgy relay?" but when I looked in the central electric box, there is no relay for the headlights, which I find a little strange because the foglights have relays?

Does anyone have any ideas on why the headlights (when switched off!) would cause my problem?

uptheorg

Radio noise only when turning! The radio is stock and plays fine when the car is pointed straight ahead! When turning, the cd's continue to play, but the sound is distorted and static is introduced at the same time. This happens whether I am turning to the right or the left, or even at a strong "bend" in the road. When the car straightens out again, the sound returns to normal. Any ideas???

dutchcrunch

i had this problem as well, using the factory din with mcintosh head unit. i drove me crazy. finally i fixed it. this was adressed by porsche on our cars with the factory installed unit too. to make a long story short, you need to ground the factory amp under the seat to the car frame and not to the wire harnesss as they have it. i did not cut any wires just made some jumpers that tie the power wire from the harness and a jumper from the amp to the ground stud thats already under the seat, it fixed the problem . I was going crazy tryiny to resolve this. but all is well.

Makmov

donno.... donno if my stero, which looks killer, even works. Never turned it on, ever, to this day.

uptheorg

Thank you so much DUTCHCRUNCH! That sounds like the ticket!