tys

Yesterday, I (with a lot of help from my cousin) installed an amp for the front speakers and an amp and x-over for the rear speakers and subwoofer tubes. The system sounds great but I get this whining noise (not my wife telling me to turn it down) that changes pitch when the engine revs up.

I am very new to installing equipment, but I think that we did a decent job of everything. Why is the interference noise happening? How do I get rid of it?

Any help is appreciated! Thanks

HorstF

Hi

The noise comes from different
ground potemtials (sorry for my
English, I'm from Germany). You
have to be sure that there is a
maximum voltage of 100 mV between
several ground points (radio, amp, ...)
The best way to get rid of noise
is to get only one ground contact, e.g.
under the back seat, where the safety belts are mounted.

Hope that helps.

Rgds
Horst

tys

Thank you Horst (your English is fine, my German is terrible)
So far, I have run a ground wire from each of my amps (one under the passengers seat and the other under the drivers seat) back to the ground wire in the factory harness of the radio.

So instead, I should run the ground wires from each of the amps to different gound points? or do you mean that I should ground both of the amps to the same point?

Thanks a lot for the help, the noise is driving me crazy!

dru

If memory serves, by running your grounds back to the factory ground in the harness, you've introduced what they call a 'ground loop'. To avoid these, make your ground wire from each amp as short as possible. Also, make sure that your signal cables (from the HU to the amps) are as far away as possible from the power cables.

Hope this helps

HorstF

Yes, thats it. Just put all your ground wires to one point and that will help.

tys

Thanks Dru. I'm learning hoards! Tonight I'll try a short wire from amp to somewhere. Are the seats grounded? I'm guessing so but there's obviously a lot I don't know. Also, how do you guys usually attach a wire to a metal part (i.e. seat rails, frame, etc...)? Do you just drill a hole and tap a screw into it or is there more to it? I assume that whatever paint is on the metal should be removed for a good contact.

tys

Thanks guys, I'll try that tonight. At least I didn't fry anything!!

HorstF

I fixed my ground wire to the screw where the safety belt of the back seat is mounted in my old Nissan Micra. I'm not sure if there is also a point for this in the P5 but I think so. Then I went with the cable to a "golden" distributor from where I provided all of my equipment with ground.

mazdaspeedwest

Right, the OEM radio ground wire is 16-18 gauge as best and can not handle the needs of an amplifier, let alone 2 of them + the radio.

and also as stated, run power and signal cables as far apart from each other as possible. I'd suggest running the power down the drivers side and looping around behind the seats to the other amp and then running the RCA signal cables down the passengers side, but looped infront of the seats to the other amp.

I suggest, since your amps are under the front seats, and to keep the ground wires as short as possible, ground each amp to a seat bolt, yes they are a chassis ground and a good one at that. Use the same gauge wire as you used for the power, which should be a 4 gauge wire, and then split into two 8 gauge wires going to each amp. But atleast an 8 gauge if not 4 gauge. The seat bolts are hefty and will require a large ring terminal, if you can't find one that fits, maybe look for a smaller factory bolt in the center console (once removed), i'm sure you'll find one there, but if not, then go ahead and shoot a self tapper into the chassis metal. Then use a regular thick/coarse threaded screw, as i find the self tappers don't hold very well. Also use a start lock washer or some type of lock washer and make sure to scrape the area clean of any paint, you want bear metal.

Good Luck!

tys

Thanks a lot guys! I'm just about to head over to Radio Shack/Canadian Tire to pick up wire and would have bought too small a wire if I hadn't stop by this site to check.

I'll make sure that I groung things properly first. Hopefully that clears up the noise. If that doesn't work, it looks like I'll have to undo/redo all the neat wire tucking that I did on Sunday.

Again, all the help and info is greatly appreciated!

JDMstuff

To make sure you have a good ground, make sure that you remove any paint from the area you are screwing the terminal into, it should be bare metal. Use the same gauge wire as the power cable and it shouldn't be any longer than 18". If you still have noise, you can run a "phantom ground" which is basically running a small ground wire from the chassis of the radio (not the one on the harness) to the amp itself. I would also check your signal cables, try not to use cheap RCA cables as this is a primary source for noise. If you do have to pass over power cables with the RCA's make sure that you do so at a 90 degree angle. If all else fails, it could be your alternator. Have the voltage regulator checked out, it can be a source for all the noise you're getting. Whatever you do, don't use a noise suppressor, those are only temporary and the noise will eventually come back.

tys

I ended up stopping by Kromer Radio (Toronto) and the guy there was really helpfull. He checked out the car and gave me a lot of tips.

I ended up running a 4 gauge wire from the battery, through the firewall and along the drivers side door to under the drivers seat. There's a great white oval plastic cover just behind the battery on the firewall, I just drilled a hole and ran the wire. I split it there to 8 gauge wire to power each amp (one under either seat).

For ground, I used the right rear seat bolt of the passengers seat. I should have used one of the left bolts so the wire isn't visible, but I'll fix that later. I ran a 4 gauge wire from the bolt to a splitter and then 8 gauge wire to ground each of the amps.

I then removed the now unused power and ground wires. The noise is gone, mostly, I think. I think that I can still hear something if the radio is on but the volume is only 1 or 2 notches above being off. And it's only with one weak-ish FM station. I'm probably being too picky.

I really have an itch to redo it all. Relocate the amps + crossover to the trunk and fix up all the connectors. Probably unecessary but it's probably a good way to kill a Saturday or Sunday.

Thanks again for all the helpfull advice.