Another stereo whining question

fewman · 02-03-2006, 03:22 PM

So here's the deal. I had my amp installed (purchased from forum member here) at Best Buy along with the power for my car computer and an alarm. They placed the amp under the driver's seat and the computer under the passenger's seat. When I first started driving, there was terrible engine noise coming only from the rear speakers. I took it back to Best Buy where they shaved the ground spot better and cut the wires (on the amp) obscenly short. Now, when I start the car there is very loud engine noise in the back and front speakers that remains until windows is halfway through loading, at which time the severity of the whining goes down substantially, and is, once again, only located in the back speakers.

This happens regardless of whether or not the car computer is plugged in, and regardless of whether or not the RCAs connecting the computer and amp are plugged in. I have ground loop isolators installed on the lines connecting the computer and amp. The Best Buy guys say that the problem is most likely isolated in the amp, and that a ground distro block would not solve anything (grounding the amp and computer together).

What do you guys think? I have pretty much lost all faith in the guys at Best Buy so I am planning on taking this on my own.

Will Albers · 02-03-2006, 04:06 PM

Thats going to happen with windows booting. Mine does that as well. You need a delayed turn on for your amplifiers to turn the amps on AFTER windows boots. Its a floating ground loop.

In regards to the noise continuing... You have an amp that is powering the rear speakers and the front is off of a head unit? In that case, again, you have a ground loop with the amplifier. Get a ground loop isolator or start doing some research on eliminating ground loops.

RedGTiVR6 · 02-03-2006, 07:07 PM

for the turn on issue - power supplies exist out there that have turn on leads that are designed to send a turn on signal to the amps after a few seconds...

on the noise - what will said

skeeter007 · 02-03-2006, 07:20 PM

I had the same sound issue you are having with your system. I tried over and over to get the noise to go away, but I couldn't completely eliminate it. Eventually, I purchased a BlueGears X-Mystique sound card and an Alpine PXA-H510 DSP. The X-Mystique has a Dolby Digital Live encoder with optical output, which I connect to the Alpine DSP which decodes the optical signal. This solved ALL of my noise problems (I don't even have noise when the computer is booting). I purchased the Alpine DSP off eBay for $200 and the sound card was around $80 from NewEgg.

RedGTiVR6 · 02-03-2006, 07:26 PM

heh- that's the main reason I went with the H701

some people can put up with the smallest amount of whine, I can't...

fewman · 02-04-2006, 03:37 AM

The amp is powering all four speakers. Why did the loud whining on the front speakers only start AFTER they cut the ground shorter? Do you think they did something else? I don't have a headset, and the whining is in the back speakers regardless of whether or not the computer is even in the car, it is still present in the back speakers no matter what. And as I said earlier, there are ground loop isolaters on both sets of lines. Do I have any other options to get rid of the whining in the back speakers?

scott_fx · 02-04-2006, 04:15 AM

how is the connection on your battery? is it clean? how is the grounding strap to the chassis? this may not cure your problem but it wouldnt hurt to clean those up (or upgrade the strap at least) That is a big prob. with corvettes and upgrading the ground and power wires (at the battery) fixes a lot of little gremlins.
can you borrow another amp and hook it up to see if it's a problem with the amp internally? are you in socal? i have a few amps laying around

you never said if you're powering the front speakers off the head unit or the rears or if you even have a headunit. we need some more info to help you trouble shoot. if you have them all powered off the amp, what happens if you switch the front and rear rca's? does the noise stay at the rear speakers or do they switch to the front?

fewman · 02-04-2006, 04:23 AM

Scott, the amp is powering all four speakers. I don't have a headset. For whatever reason I never tried switching the RCAs on the amp, I will try that in the morning!

RedGTiVR6 · 02-04-2006, 08:25 AM

let us know about the RCAs

are they the cheap kind or did you fork over at least a bit of money for them?

fewman · 02-04-2006, 05:54 PM

Should they make a difference? When they are completely disconnected from the amp and the computer, it still makes the sound (disconnected on both ends -> still noise.)

RedGTiVR6 · 02-05-2006, 12:59 AM

that tells me that you are getting induced noise in your speaker wire

you should check the runs....speaker wire shouldn't be running next to any electronics...that's if it's just a hum

does it vary with the engine RPM at this point?

Will Albers · 02-05-2006, 11:23 AM

He has a built in amp. I have never seen speakers pick up enough interference to cause audible whine. That just requires too much amplification to hear. Somewhere he has a stock amplifier. I would disconnect the wires at the speakers and toss some new speaker wires over the seats. Test a direct connection.

I'm betting my 50 cents that the installers never bypassed the stock amplifier!

Legarcondemerde · 02-05-2006, 11:34 AM

Hmm...I definitely agree with Will, that would certainly cause some noise issues if the lazy bastards didn't bypass a factory amp. What kind of car do you have?

RedGTiVR6 · 02-05-2006, 02:22 PM

if they didn't, I'd take it back and throw a fit!

fewman · 02-05-2006, 02:31 PM

I honestly don't think there is a built in amp. It's an 2005 elantra gt. I will look it up to see if it has a built in amp. Where would it be (usually)? The whining does go up with RPMs, and does not exist when the amp is disconnected. I will test a direct connection between the amp and the speakers later today.

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