noise from rear speakers, please look at video

sanbas · 09-23-2004, 10:48 PM

Here is my situation...now that i have bought all the parts necessary for my carPC to work with my amp in my '01 diamante LS and plugged in everything to see if it work i am getting NOISE. BTW I am going Headunitless for my audio, i am going to put a 7" monitor where the double din radio is right now.

Here is a pic of the setup:

Using a MSI Mega...its plugged in from an extension cord from the garage.

Here is a link to a video and audio of the noise (the audio is kinda breaking up towards the end of the video, thats just the camera):

if that doesnt work copy and paste this on your URL:

THIS IS THE SITUATION I AM IN:

1) The noise ONLY comes from the rear 2 speakers, if i disconnect them then there is NO noise and the music sounds perfectly clear from the 6 front speakers.
2) I bought a ground loop isolator (~$20 tsunami brand from circuit city), adding that didnt help at all with the noise.
3) I also put in a Sound Blaster 5.1 Live for audio, instead of the integrated sound card...that didnt make any difference either.

Any suggestions would help...

Some other stupid questions i have are (1)why do many of these thread say "bump" in the middle? (2) when you say use "acc" for power, is that accessory 12 volt?

Thanks

If the video link doesnt work then let me know.

P.S. I might not have the car for the weekend (going to the dealer while its under warranty

), while i was doing that i messed something up and now the keyless entry, memory seats, factory radio wont work and my digital trip odometer resets to ZERO every time i turn the car off.

Sorry for the long description, wanted to be clear.

P.P.S. my last post was http://www.mp3car.com/vbulletin/showthread.php?t=32350
atleast i am making progress

ppgt94 · 09-23-2004, 11:23 PM

Since it's only your rear speakers could be a bad connection/ground in the sound card or amplifirer/head unit. Gosh...noise could be a million things. Eliminating possibilities one-by-one is probably the best thing to do right now. Especially since your car is still apart. Try the sound card, amp, check wire connections, etc.

Bump means to "bump" a thread to the top of the list of new posts. Some people use "TTT" which means To The Top.

Yes, ACC is usually a reference to the accessory 12v line.

sanbas · 09-25-2004, 12:12 AM

I am bypassing the head unit, my setup is this way EXACTLY:

Music from Media Player >> PC Sound card >> RadioShack RCA to 1/8 jack >> Metra Ground Loop Isolator >> Metra Amplifier Integrator Harness (DIN to RCA) (also have a blue wire from the Metra harness going to 12 V acc>> Stock Mitsubishi Amplifier >> 8 Speakers >> Music coming from all 8 speakers, noise included from rear speakers only

1) all my wire connections are tight
2) I dont have any special grounds. Or even know what size wire to use or what to ground.
3) do i need to ground my amp? its coverd in plastic.

Ground my PC??? I have heard people saying ground your PC, but have never really understood it. If you all could be more specific? can i just put a wire on the case somewhere and then the other end to metal on my car?

Thanks

Joe_Collectible · 09-25-2004, 12:59 AM

Ok, well first off you should know that some vehicles require the factory radio in order to power other vehicle functions.... In some cases, you cannot remove or bypass the radio and instead have to relocate it. It is hard to see if you left the radio wiring harness attached to the radio itself and used the factory harness to attach your "new" speaker level output. If you did, you wouldn't have any problems... In other words, your radio should still be hooked up, but not the speaker + and - (those would be hooked up to your speaker level source) - if your using that blue remote wire, surely you must have the harness attached already.

As for your car... Disconnect your battery for at least 3 minutes (check manual for cpu reset times), connect your radio harness back to the radio and re-connect your battery.

As for the noise only do as I say if my assumptions are true.
I assume this is the order of your input series: pre-amp (soundcard) -> RCA -> input on amp -> speaker line level (+ & - for each speaker)
-> factory speaker wiring.

(no g-loop isolator yet) errr, remove it!

Try this: First thing to do is move a good sounding channel's rca to make sure that it is not the signal.... If one of the "good channel" rca causes noise in the bad channel's place, you can go from there. If no noise you may have a bad rca or input signal from the original source which caused the noise. If you still get noise, you would then want to swap the speakers that were noisy onto an already proven "clean" channel at the amplifier's speaker output terminals...

lemme know what happens

Good luck - and I hope the warranty covers

anode · 09-25-2004, 07:46 PM

I'm sort of in the same boat. I was using an iPOD in the car plugged into a kennywood amp. Worked well. Swtiched to the carputer and now I get noise. The level had to be trimmed down a lot too (iPOD was 'quiet', carputer loud)

Now, I'm thinking its an impedance mis-match. The input of the RCA's on the amp are 10K, and a set of headphones, I would think are down in the 8ohm-ish range. I haven't measued a pair yet. So maybe an impedance matching xformer might be in order. Or down and dirty just a resistor.