Audio Guru's I need your help.
 

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?

http://www.b40huckers.com/0504081441.jpg

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.

was the filter for the ground or power wire?

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?

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

http://mobile.jvc.com/features/regul...on/feature.jpg

RCA connection straight to the amp.

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

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.

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

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.

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.

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.

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.

http://forums.pelicanparts.com/uploa...1210001438.jpg
Deck installed...all of the noise issues came with the amp install as the deck worked perfect before with just the infinity powered sub.

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!

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.

http://forums.pelicanparts.com/uploa...1210026879.jpg

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.

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.

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.

This is what im talking about. http://www.crutchfield.com/App/Product/Item/Main.aspx?g=761&i=127BB6&search=bass+blockers&tp=3 216
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.

Yep that's it.

IF you get 'em, though, get the 1,200. even that seems REALLY high.

Or maybe pm brian (bell) and he could probably tell you a capacitor value you could go to your local Radio Shack and get the same thing, but at a lower (Hz) value. For example, if your subs cross over at 100 HZ or something, then you get a cap (bass blocker) that will corner at 100 Hz as well, to match.

How would i tell where my subs cross over. I'm not very well informed on that type of thing

the crossover points do not need to be matched number for number, for your 4x6 speakers (assuming they're 4ohm) will work good with a 100mfd capacitor (this will crossover at 400hz), remember that a cap on it's own will only crossover at -6db per octave, so 2 octaves down at 100hz it'll be 12db quieter. caps will eat up the available power though so you will lose some efficiency.

if you're buying a new alpine make sure it has a built in high-pass for your 4x6's, it'll sound 150% better than using caps as it won't be wasting power.

check out this site
http://www.bcae1.com/passxovr.htm
it's got a good general description of what caps and coils do at different impedances.

your sub crossover should be built into the amp, but again, don't go by any specific number, use your ears and a few of your favorite cd's to tune, every car is different when it comes to harmonics.


and yes you can buy raw caps from the "shack", you'll want non-polarized caps with the value you want (100mfd), just be sure to insulate the exposed wire coming out of them so it doesn't short out.

Ok i think i understand now. This is the deck I am looking at
http://www.crutchfield.com/App/Product/Item/Main.aspx?g=300&i=500CDA9884&tp=5684&tab=features_ and_specs But I am not stuck on alpine. I just know how to use them so I thought i would stay with one. Anybody know of anything better that does about the same for less than 200 bucks. also does that one have the high pass thing for the 4x6s that Bell mentioned.
Thanks for the help guys.

YES that deck does have it. Look on page 14 of the owner's manual. So, if you run the sub-out to your amp and 12s, and then run the 4x6's off of the deck and use the 'high-pass' function, you should be reasonably happy, for the money.

And then, go to the 930 forum and search the term "slippery slope" and see if it applies to the way you feel about stereos. :D:D

the alpine does have a hp out for the speaker outputs, so yes that would work well, i do know the alpine menu system is a strange one to navigate so you'll need to read the manual a few times :D

You mean theres a manual. Is that what that little book i always throw away is called. Thanks guys. I will pull the trigger on that deck and a new pair of blaupunkt 4x6s once o get the body shop bill paid off.

Manuals are your friend; be nice to them. ;)

coincidentally i put that same alpine in a subaru today (cust bought it from crutchfield too), seemed like a nice radio and sounded good on the stock 6.5" speakers :)

DO NOT buy an Audi!!!

Oops you typed Audio.

Never mind.

:D

Good to hear that bell. I am more willing to spend the money if i have heard good things about something. So dont worry Jim I wont buy an audi.

BTW good trick I learned...use a zip tie to snake wires through factory boots to the doors or through the firewall. I was amazed at how easy it was to push the zip tie through and tape/pull the new wires back through.

Yup that or an electrical fish tape or small copper wire. My dad has a sign shop and you learn very fast what makes good for fishing wires when you are 60feet in the air. I was planning on running all new wires with the new stereo. That should help the audio quality tons.

Oh how are you liking the alpine amp. I think i am going to downsize my stereo setup and might look at alpine when i am buying an amp.

Oh btw here is what i am downsizing from. Anybody have a guess at what i could get out of it. I assume that 1200w ampwould be too much if i went to a pair of 8s.
http://forums.pelicanparts.com/uploa...1210290615.jpg

The Alpine amp is very good for the mids and highs, excellent quality of sound...even when I had it in my old 911.

here are some pics of a "stealth" install i did in a 944 :)

this was VERY LOUD, if i ever get a 944 this is how i'll do the bass....who really needs a spare tire :D
http://forums.pelicanparts.com/uploa...1210296670.jpg
http://forums.pelicanparts.com/uploa...1210296689.jpg

Thats cool but where i live i need to have the spare with me soo. I think i will build little boxes to drop in those holes on the side in the back. I have read before that an 8 will fit in there. What brand of 8s would you recommend?

MB Quart