weird ringing sound after amp install.

[Xenozx 10+ year member]

THE SOUND

http://www.xenshardware.com/images/Evo2009/MVI_1921.avi

OK, so I had a cheapo pioneer 60w x 4 @ 4 ohm amp. It sounded crappy even w/ the gain maxed so I was told by an audio shop, i was under powering the speakers and to look at something in the 100w RMS range. He suggested the PDX 4.100, and I looked it up, saw it had good reviews and went with it.

So I installed the PDX in the same location as the pioneer was. I used the same ground and power location, only difference is I switched the 8 gauge wiring to 4 gauge.

reused the same RCA's and remote wire.

you can hear the noise even when the car's engine isnt running. That first sound, its my boost gauge, it makes that really loud noise every time it boots up, so please ignore it, its that constant ring sound that never goes away.

I tried 2 other ground locations and still have the sound (seat belt bolt, bolt that holds the drivers seat to the floor of the car, and a bolt direct to metal frame of car). I sanded before I put the grounds down.

power runs directly from the battery. I have an JL amp that is powered by the same distro block that does not seem to exibit this same problem.

Sound comes from all 4 speakers. Have tried discoing 1 speaker at a time, and sound stays no matter which one is hooked up.

Sound does get louder the higher I put the gain.

there is a switch on the amp 1+3/2+4 - 3/4 - 1/2 And I have it set to 3/4 (Set this switch to “3/4” to have the inputs of CH-3/4 accept independent input signals. An example of this application would be

the use of a head unit with dual pre-amp outputs).

I have tried all 3 settings though.

I have tried HP and LP filters, and also shut the filters off. Sound remains in all three, when set as a LP filter, it is muffled, along w/ all the sound from the speakers.

I thought it was the amp, so I RMA'd the amp, and now have a 2nd Alpine amp and its making the same sound as the first one.

Any ideas what could be causing this?

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[Wingman0121 10+ year member]

Bypass your headunit, get a portable CD player and a headphone-to-RCA adapter and plug it directly into the amp, turn on the amp by jumping a wire from 12v to remote and see if it makes the same noise while playing music.

 

[Xenozx 10+ year member]

I did as you said, and the sound is perfect when running my personal YEPP MP3 player directly to the amp and powering it by both the wire from the 12v and by the remote turn on.

so this definately points at the RCA's/head unit as being the culprit. Any idea what exactly could cause this from the head unit side of things? I didnt change anything and I didnt have this problem in the past.

 

[Wingman0121 10+ year member]

It could be a few things especially if it didn't make that sound before. Perhaps the RCAs went bad, a lot of times they get pinched/stuffed behind the dash and overtime the heat/vibration catches up with it and might of frayed the wire. It could also be a ground loop noise(not sure if the noise changes pitch with your engine RPM or other stuff like A/C or defrost?). Another thing I can think of is the actual circuit inside the headunit, maybe a capacitor is going bad in the power supply or the preamp stage.

Try running a new RCA cable, if that doesn't help then see if you can swap the headunit out with another one that you know it works. I know it's a pain but it's the only way to make sure.

 

[Xenozx 10+ year member]

OK, i rewired my whole car, double checked every connection. Still have this stupid whine.

Now, I noticed that if i touch the center conductor of the RCA cable to its shield the noise goes away.....

WTF does that mean?

Like, I have the amp w/ no RCA's in it, and have no whine sound. I plug the RCA's into the back of the amp (the other end is not connected to anything) and the whine comes (sometimes) it almost seems dependant on how long the RCA cable is, the longer it is the worse the whine.

Anyway, if i take the other end of the RCA that is currently plugged into the back of the amp, and I use a screw driver, and I touch the conductor to the shield, guess what? The whine goes away....

What on earth does that mean?

 

[Wingman0121 10+ year member]

Hum... okay try this, instead of hooking up the RCA cable from your headunit to the amp, get a set of headphones and a RCA to headphone adapter and plug it directly into the preamp outputs and see if you can hear the noise in the headphones.

I suspect a ground loop noise somewhere. Not too often does a headunit's internal circuit goes defective, but I've heard this kind of stuff happening on Pioneer decks... something with a pico diode or something.

 

[Xenozx 10+ year member]

already done, when I use my MP3 player, no problems //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

I too suspect a ground loop issue. I just bought 2 Ground loop isolators, and am hoping those will remedy my problem. Only issue is they probably wont be here till Thursday //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

 

[Wingman0121 10+ year member]

Ya I've used a mp3 player as my headunit in my car for the longest time because my CD player can't cope with the bass, it is just as loud without any skips so it worked out.

 

[Xenozx 10+ year member]

OK round 2. This makes no sense what so ever. I am really frustrated now.

So, I was thinking my problem was a ground loop issue. I bought 2 RCA ground loop isolators and hooked them up to my front and rear pre outs. It did reduce the sound to almost nothing (could still hear it w/ the music volume totally off) except when you started the car then it got a little louder, and if you played with the throttle of the car you could hear the noise get a little louder and move w/ the how many RPMS your at.

So I removed the ground loop isolators and went to work to try to figure issue out.

I ran a brand new ground directly from the amp to the negative terminal on my car battery. (SOUND STILL THERE)

I ran a ground directly from the back of my headunit (head units ground) to the negative of the car battery (SOUND STILL THERE)

Tried grounding both the shell of my headunit and the shell of the amp, sound never changed (SOUND STILL THERE)

Rewired everything behind the headunit and taped up any loose cables not in use (SOUND STILL THERE)

Tried 5 different pairs of RCA cables, short and long (SOUND STILL THERE)

Tried to remote from the 12v power source on the amp instead of using the remote wire (SOUND STILL THERE)

Disconnected my other amp (my subwoofer amplifer) totally from the car. (SOUND STILL THERE)

RMA'ed Amplifier and got another one of the same brand/model and still have the sound (SOUND STILL THERE)

Everything I tried and this sound still haunts me. I miss my music //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif

the one thing I have been able to do is identify some how some way it has something to do w/ the RCA's, RCA pre outs on back of HU, RCA connections on amplifier. The reason I say this is if I twist/bend them the RCA's (where the preout from the HU meet the RCA cables running to the amp) or take a screw driver and touch the RCA cables center conductor to the shield i can make the sound go away. The sound is still there even when not attached to the head unit.

I had a pioneer GF-6400 before this amp, and had no issues with this sound at all, just that it sounded really crappy and was underpowering my speakers (60w RMS amp to 100w RMS speakers)

Now I have the alpine 4.100 (certificate in box says 127w x 4) powering the speakers and if I turn the music up really loud it sounds FOOKING BOSS! but that stupid sound is still there.

My headunit is a Pioneer x910BT

speakers are polk audio DB651's comps in the front and DB6501's in the back.

Anyone have any other idea what could be causing this? I think on Sunday I might go to best buy and see if they have any 4 channel amps and buy one (to return later) and see if maybe its a compatability issue between the alpine amplifier and my car setup?

 

[joe98chevy 10+ year member]

im just curious did u buy that pdx brand new?

 

[Xenozx 10+ year member]

yea, I bought it from 6ave electronics, and when I tried round 1, and assumed it was the amp, I called them, ordered a 2nd one (so I would get it quicker) and they sent me a label for the 1st one so I could send it back for a refund. So once i got the 2nd one new in box, and hooked it up and still had the sound I was pissed. Couldnt figure it out for the life of me.

 

[Xenozx 10+ year member]

i see the alpine amp is 10.5v input, and my headunit is 2.2v output, does that make a difference?

 

[jeyventura 10+ year member]

are those rcas you are running the ones in the picture ???? from monoprice

 

[Xenozx 10+ year member]

ya, those are from my computer tho, i only used them for the MP3 player hook up, the RCA's I tried from the headunit to the amp are brand new Scoshe RCA's. I also tried 3 other sets of RCA's that came w/ some 2000w amp kits I bought.

 

[jeyventura 10+ year member]

dont use those thats your problem there your rcas are picking up noise some people get some dont i was like that before i have about 5 sets of rcas running on the same place and it was horrible before i got some shielded ones go to HDMI Cable, Home Theater Accessories, HDMI Products, Cables, Adapters, Video/Audio Switch, Networking, USB, Firewire, Printer Toner, and more! and pick up some or ask here for some monster

Thats your problem there im 100% sure