alternator whine from F/R preouts but not SW preout

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Mon Oct 05, 2009 6:33 pm

as the subject states, Im getting alt whine from my F/R pre outs but not the SW pre out. The F/R pr eouts plug right int the back of the deck where as the SW pre out has a 2inch lead with female ends on it. Am I recieving interferance from the deck on the F/R pre outs? I think I remember SMGREEN having this problem and the quick fix was he soldered a 14-16 gage lead to the rca's?

Feel free to chime in with your .02 cents, thanks guys

Post by **mhyde71** » Mon Oct 05, 2009 7:47 pm

I would go with that suggestion and see if it works...
reason for not getting out of sub, at least imo is b/c of the frequency. Those/that should be a pretty high freq and prolly wouldnt be able to hear thru the subs. JMO/thought(s), I had same thing, and as soon as I grounded the RCA's to HU i was golden... happens to be a famouse issue on pioneer units... not sure if any others, but i know on the Pioneers HU it is a common problem.

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Mon Oct 05, 2009 7:52 pm

I guess it was you matt

so how did you ground the rca's to the head unit? I dont have the cash for a new HU so the quick fix will suit me just fine, could you elaborate please

Post by **mhyde71** » Mon Oct 05, 2009 9:09 pm

connect to outer sleeve (neg) shield of rca, and simply attach to screw in the chassis of the HU.. you can test the resolution/theory by first doing it to an rca at the opposite end (going into amp in back) and grounding to chassis of car... just to make sure that will even help before ripping dash apart- lmk

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Mon Oct 05, 2009 10:53 pm

sweet dude thanks

HoseHead · Post by **HoseHead** » Tue Oct 06, 2009 4:49 am

One possible reason why your getting alternator whine is you have a potential difference between the different devices in your system. Matt's solution works as it is essence, creating a single point ground. And yes, higher frequency noise would not be "heard" at the SW O/P as it's band pass is probably set lower than the induced alternator noise frequency.

When designing a system, it is best to have two distro blocks, one for B+ and the other for ground. Home running all grounds back to the ground block ensures all devices are using a single point ground and therefore eliminating any potential voltage difference between devices. This voltage difference, even very small ones, is what creates noise. Perhaps adding a second ground distro in the front of the car for the dash components is easier as long as that block is connected to the "host" block in the rear using a large gauge wire (4 AWG). Single point.

Grounding your HU and other processors to the vehicle chassis at the front of the car while your amps are connected to another point on the chassis at the rear of the car MAY create a potential difference. The vehicle's chassis MAY have electrical resistance so the components MAY be fed slightly different voltages and therefore induce noise. With all the composite plastics and other non-conductive materials used in cars these days, this phenomenom is more likely.

It is also recommended to add grounding straps between the vehicle's engine, body and chassis. Factory grounding is, at times, not good enough for high performance audio systems. Investing in a quality power/ground distribution system is criticial in maintaining a constant voltage to all devices in your system.

HH

Post by **stipud** » Tue Oct 06, 2009 7:32 am

Are you running different RCAs for the sub/f/r pre-outs? Or the same one? The issue could be the cable itself.

Post by **smgreen20** » Tue Oct 06, 2009 8:01 am

I want to eliminate the ground loop theory for the reason that the amps themselves would induce the noise regardless if it's a sub amp or the F/R amp. The noise, In my opinion, is from the RCA signal side of things. That's why the F/R amp isn't filtering the noise, but the sub amp is.

Switch amps for a bit. Hook the sub amp up to a mid and the F/R amp to the sub and switch the RCAs too. See what happens and let us know.

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Tue Oct 06, 2009 3:41 pm

stipud wrote:Are you running different RCAs for the sub/f/r pre-outs? Or the same one? The issue could be the cable itself.

ive used multiple ones, the thing is this just popped up one day, its not the greatest hu either, its a cheaper kenwood.

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Tue Oct 06, 2009 3:46 pm

smgreen20 wrote:I want to eliminate the ground loop theory for the reason that the amps themselves would induce the noise regardless if it's a sub amp or the F/R amp. The noise, In my opinion, is from the RCA signal side of things. That's why the F/R amp isn't filtering the noise, but the sub amp is.

Switch amps for a bit. Hook the sub amp up to a mid and the F/R amp to the sub and switch the RCAs too. See what happens and let us know.

tried this already, nothing changes

ive got some time this weekend to see if i can fix this.
Im going to try Matts method amd see what happens.
If you guys have any other ideas feel free to chime in. thanks in advance for everyones help

Post by **ttocs** » Wed Oct 07, 2009 5:03 pm

what kind of deck? Try running a 2nd set of rca's above the carpet and see if it could be a cable.

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Fri Oct 09, 2009 3:13 pm

mhyde71 wrote:connect to outer sleeve (neg) shield of rca, and simply attach to screw in the chassis of the HU.. you can test the resolution/theory by first doing it to an rca at the opposite end (going into amp in back) and grounding to chassis of car... just to make sure that will even help before ripping dash apart- lmk

We have a winner

Thanks Matt this worked like a charm, now im off to install some amps

Post by **ttocs** » Fri Oct 09, 2009 4:32 pm

its funny how often that works but remember that it is a band-aid for a bigger problem. It could be the output, or it could be the rca cable.

try a temporary cable just to see if that takes care of it as well.

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Fri Oct 09, 2009 7:01 pm

ttocs wrote:its funny how often that works but remember that it is a band-aid for a bigger problem. It could be the output, or it could be the rca cable.

try a temporary cable just to see if that takes care of it as well.

Update.........

It was fixed and now its fucked again

TTOCS I dont like to patch shit, but I gave it a shot, it worked now its the same whiney bullshit. Im perplexed on this sitch, more troubleshooting on the way stay tuned

Post by **ttocs** » Fri Oct 09, 2009 7:49 pm

I ain't sayin leave it like that man just run it above the carpet or around the car and hook it up fer a few mins and you will know if its the rca and if you have more work to do either running cables or troubleshooting.

Another way I have had limited success with is to run the decks ground cable back with the rca's and remote wire, and ground it at the amp. This way the deck and amp have the same ground.

now just curious, have we started super simple and checked the decks ground and such?

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Tue Oct 13, 2009 4:17 pm

update...... I tried your RCA's over the carpet ttocs, and it was the same

I also checked the decks ground and it was good aswell. I guess the other day I was so choked that I forgot about the ground switch on the MS275, it was on flat, so Iswitched it to common, still alt whine, then I tried Matts meathod with the jumper from the RCA to the deck and......

TOUCHDOWN

S o I just finished listening to a whole bunch of cd's, from James Newton Howard and Friends to Dr.dre to fiddy cent and Jamariqui and finished off with some Rage Against the Machine. This amp is phoenominal tons of headroom and power and cleaner than a virgin, now all I have to do is figure out where to mount my EQ215X. Im also probably going to use my M amps in my house set up

Thanks to everyone for all the help

Post by **mhyde71** » Tue Oct 13, 2009 8:54 pm

so has the whine gone away or not? i am confused... heard it was gone, then back, and now a thumbs up...

fill me in... I 'm lost

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Wed Oct 14, 2009 12:47 pm

long story short.....ITS GONE

Post by **mhyde71** » Wed Oct 14, 2009 12:50 pm

omg i just looked closely at your avatar - whoooa dood! thats messed... and messy

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Wed Oct 14, 2009 12:57 pm

I chose the avatr strictly for shock value

your the only one to comment so far