Miata Installation

I installed my MKII into my 2001 Miata using an MTX 4 channel amp. I also installed a JL Audio 8 inch sub under the passenger side wheel well and infinity separates in the doors. All is fine except that I have this alternator whine that drives me crazy when listening to soft passages or to a talk radio station. I am sure there is a ground loop somewhere, but the installer did ground both the amp and the HU to one grouding point in the trunk. I also have the radio module, BTW, and a power antenna. Finally, the whine gets worse when i turn on the A/C!

any and all help will be appreciated!

You're going to need to go through the ground loop troubleshooting steps in the FAQ... But first... Is the amp gain adjusted right? Can you turn your player all the way up to 0db without distortion?

Also, since you know it changes with different items turned on / off (the A/C), be extra certain that the RCA cables leading from the empeg back to the amp aren't on or near any noise sources - as in, make sure the cables aren't running under the dash right next to the fan motor, as an example.

That would be my personal first shot - maybe even take the empeg out slightly and connect another set of patchcords (something from a VCR would even work) drooped over the seats right to the amp itself. See if the new path stops the noise.

Second, I'd check the ground point itself. There's been at least twice I can remember where I grounded to a metal object in the car, that turned out not to be a ground... Make sure you're grounded to the chassis of the car directly, and that you use a star washer or some other method to make metal to metal contact.

After that - if there's still noise, definitely go through the FAQ step by step.

Make sure you're grounded to the chassis of the car directly, and that you use a star washer or some other method to make metal to metal contact.

Star washers are a must-have. I'd just like to add that it's also important to scrape the paint down to bare metal (protect with petroleum jelly) at the earthing point.

Additionally, it's a good idea to run the player on the seat in case it's getting a 2nd (unwanted) earth in the dash.

Actually I went through the troubleshooting guide many times. The power leads run down the passenger side of the car and the RCA's run down the dirver side of the car. I sanded down to bare metal the ground point in the trunk and fastened it with a star washer.

The dash of the Miata is very compact and I am sure that the RCA's are running very close to the fan motor. I will see if I can re-route them away from it.

I even tried grounding the sled separately, and checked to see if the ground wires in the harness were secure, they were, and the extra grounding made no difference.

The battery is in the trunk of the car, only a few feet from the ground point. Do you think this could be a cause of the problem?

My last hope is to install a noise filter in line with the alternator. I already installed this massive noise filter I got from Crutchfield that goes between the battery and the amp. There is also a filter between the RCA's and the amp as well.

To make matters worse, the installer swapped out the Rio for a Sony unit and we found the noise practically disappeared!!

Alas, doomed to have a perfect system in an imperfect environment!

Help!!!!

As a test, with the player in the sled and on the seat, try grounding one of the AC RCA shrouds. Unfortunately, this was the only way I could cure my ground loop.

Thanks! How would I go about doing that? Would I have to do it at the Head Unit or could I ground them into the amp, which would be a bit easier?

Did this solution cure all of your ground loop whine?

I don't think you should aim to install an additional permanent earth until you discover what (if anything) solves or improves your problem.
Out of desperation, my approach was to have an additional flying earth lead with a bare end and start grounding various parts of the system to see if I could make an improvement. I soon found that the only places that helped were on the empeg itself, not the sled nor the sled wiring.
For me, the best result was at pin-5 (GND) on the serial connector - silence! It was impracticle to implement this permanently but I found that the outer shroud on the AC RCAs were a 2nd best. To achieve an installed fix I used a short strip of metallised foam gasket stuck inside the sled at the rear - when the empeg is docked the RCA shrouds ground against the mesh. This gasket material is often used to provide RFI shielding in electronic enclosures - I robbed my piece from an old PC

...so you grounded the rca inputs on the back of the unit itself, and not the rca shrouds on the patch cord leading to the amp in the trunk?

...it sounds like the mesh you installed forced contact between the rca inputs on the unit and the sled, thus grounding it...do i understand this correctly????

Yes, you understood me correctly on both points

When the opportunity presents itself I will put up a picture of this bodge

Edit: Typo

i guess then that i could conceivable use steel wool or something to that effect to equal what u did?

Well, first of all you need to use the flying ground lead technique so see if this approach would benefit you.

I would be concerned about small pieces of steel wool breaking away and causing short circuits, like I said, most electronic/computer cases/cabinets seem to have this type of gasket material.

thanks for the tip...it will be my project over the weekend....this is really getting frustrated and i bet it is a very simple solution..my gut says that i am running the RCA's to the amp too close to the other wiring in the dash and i am picking up some noise that way.....or that there is something wrong with the unit....

I think perhaps you should sell your car, buy another, more empeg friendly car, like say, an audi tt, reinstall and be done with it...

HaHa

I'm afraid that the TT would get the last laugh. Trust me, the TT is NOT friendly to aftermarket stereo modifications unless you have a lot of cash and/or time.

*ahem* Sorry, back to the Miata discussion...

Well, truth be told, I simply adjusted the gain on the amp to a lower setting, it was turned up to the max, and the whine is gone!!

go figure!!!

...check that...I should have said that when playing MP3's there is absolutely zero whine...however...when playing through the radio module the whine is clearly heard. Now...I see that Crutchfield has this antenna noise supressor...does anybody have any idea if this works or not?

Please let me know!

Thanks,

Ed

thanks for your not so helpful tip..tubby!