Audio Guru's I need your help.

[k9handler]

Today I installed an Alpine amp in my 4Runner and now I have the damn alternator high pitch noise through the mids and highs (what the amp is pushing).
Speaker wire and the RCA to the amp are not running with the power wire, and the ground is short as possible and good quality.
This amp was installed in my 911 with no issue, so how do I get rid of the engine noise? Some form of filter?

[slodave]

I can't be of too much help, but I had a '88 Scirocco and it caused my amp to amplify the engine noise. I did have a filter that worked well, it was small.

[k9handler]

was the filter for the ground or power wire?

[bell]

first question.....is there a factory radio in the dash with a line level converter to give you rca outs? or is it aftermarket radio?

[k9handler]

No its a JVC, basically this one without the GPS.



RCA connection straight to the amp.

[slodave]

Originally Posted by k9handler

was the filter for the ground or power wire?

I have no idea anymore. It was installed when I bought the car (used).

[rammstein]

From a relatively inexperienced guy (me), here's my thoughts:

-what kind of rca cable is it? If it is not twisted pair, get one that is
-double check the ground on the stereo itself

Hmm... IF those don't pan out, then maybe try this- pull the stereo out of the dash, and get another RCA and run it straight to the amp right over the seats, just for test purposes. See if you get interference in that scenario. If you do, then you've ruled out bad cables, and you've ruled out something weird with your currently chosen route. It doesn't get you a solution, but it might tell us more.

Then again, somebody will probably have much better advice than me.

[k9handler]

Originally Posted by rammstein

From a relatively inexperienced guy (me), here's my thoughts:

-what kind of rca cable is it? If it is not twisted pair, get one that is
-double check the ground on the stereo itself

Hmm... IF those don't pan out, then maybe try this- pull the stereo out of the dash, and get another RCA and run it straight to the amp right over the seats, just for test purposes. See if you get interference in that scenario. If you do, then you've ruled out bad cables, and you've ruled out something weird with your currently chosen route. It doesn't get you a solution, but it might tell us more.

Then again, somebody will probably have much better advice than me.

The RCA is twisted pair.
After I did the install and tested the system and heard the noise I did start testing.

Used the shortest ground and heavy guage wire with quality loop ends.

Ran the RCA wire over the seats away from all others, in fact installed all wires on a different path just for this reason.

Thanks for the ideas. I am at a loss.

[rammstein]

Yup- that's as far as my brain gets...

[bell]

ok......if you unplug the rca's at the amp does the noise go away?
if so pull the radio out and take a piece of wire and hook one side up to the ground shields on the rcas , and the other side of the wire you want to touch the chassis of the radio, it'll either get louder or softer, if noise goes away secure the connections and you're done.
if not try connecting it to the ground wire of the radio.
if not then try only having the center pin of the rca connected to the radio and the ground shield not connected to the radio (barely plugged in) if this fixes it then either carefully strip and disconnect the ground shield of the rca and secure everything up....

what we are doing is redirecting the ground path of the rca's to where it won't be picked up by the amps preamp section. you're in good hands......we'll figure it out

[k9handler]

Originally Posted by bell

ok......if you unplug the rca's at the amp does the noise go away?
if so pull the radio out and take a piece of wire and hook one side up to the ground shields on the rcas , and the other side of the wire you want to touch the chassis of the radio, it'll either get louder or softer, if noise goes away secure the connections and you're done.
if not try connecting it to the ground wire of the radio.
if not then try only having the center pin of the rca connected to the radio and the ground shield not connected to the radio (barely plugged in) if this fixes it then either carefully strip and disconnect the ground shield of the rca and secure everything up....

what we are doing is redirecting the ground path of the rca's to where it won't be picked up by the amps preamp section. you're in good hands......we'll figure it out

ok I will do some testing tomorrow, thanks.

[k9handler]

Started off with a better ground wire for the deck, straight to the chasis and fresh metal.
Connected wires to the ground shields on the RCA's and this increased the noise. Connected these wires to the chasis of the deck and it returned to the level as before...also tried connecting the wires to the ground and it became very loud.

So...should I try and just run a better set of RCA's to begin with? The set I have are not poor quality by any means but not the best available either.

Mind you this audio noise can only be heard over very suttle music or between songs. I think its something simple I just haven't figued it out yet.

[bell]

did you try only having the center pin of the rca connected to the radio? you can usually try this by just barely plugging it so the center pin makes contact and the ground shield doesn't.
if this fixes a ground loop isolator (rca filter) should work.

also where is the gain on the amp set, if you back it down does the noise get quieter?

i like to tune amps with the radio at about 3/4 volume then bring the gain of the amp up until you get the volume you want.

[k9handler]

I did try just the center pin on the RCA's and the noise increased.

Gain is at about 3/4 so I may try and adjust it back and tune the deck again.

Crossover is at 120 on both the deck and amp. HP filter is on (amp), and on the deck its set at through. I have tweeked these settings a bit and this seems to work best.

Front channels on the deck are at 5db and the rear are at 10db, with the infinity powered sub on its own connection.


Deck installed...all of the noise issues came with the amp install as the deck worked perfect before with just the infinity powered sub.

[k9handler]

ok I cut the gain on the amp back to .5 and matched this setting on the decks internal controls...this made the noise so quiet I had to concentrate on it just to hear it.
Further adjustments on the HP filter and crossover eliminated it or at least to the human ear.

Thanks for the assistance Bell, appreciate it!

[k9handler]

I visited the local sound shop to have them give it a listen and help with tuning the amps and deck. It cost me $17 for this and we eliminated the ground loop noise with a ground isolator connected in series with the RCA's from the deck to the amp.

[Jims5543]

My car was doing the same thing with my Sirius Stiletto car adapter.

It turned out being my Alternator was going bad, I put in a new one and the problem was gone.

Try unplugging your alternator and running the car and see if the noise is gone.

[porsche4life]

Sorry to Hi-jack but this really doesnt warrant another thread.
Does anyone know if the bass blockers that crutchfield sells are worth the 4 bucks. Also i have 4 4x6s so would i need 4 of the blockers? I have 2 12s in the back so I'm not worried about the lack of bass in the other speakers.

[Gogar]

I -think- you mean a capacitor that you will wire inline right before your 4x6. If you have 12s in the back, the answer is most definitely YES, unless your deck has some kind of Subwoofer, High-pass setup inside it. Some amps also have little high-pass pots that you can use instead.

But if you don't have those things in either the head or the amp, you wire the capacitor into the speaker cable, and it will take the extreme low end out of your 4x6s. That way, they're not trying so hard to make all that low end that they can't physically make anyway, and the low mids and mids get cleaned up considerably.

[porsche4life]

This is what im talking about. http://www.crutchfield.com/App/Product/Item/Main.aspx?g=761&i=127BB6&search=bass+blockers&tp=3216
The deck does have a sub setup but it is still throwing bass at the little speakers. I am about to go to a newer alpine deck tho.