Soul Crushing Noise

[MCShaffer]

I'm at the end of my rope, so I'm hoping someone can offer a suggestion. After my stock deck died in my '03 G35 sedan, I decided to make use of the pile of car stereo gear that I've had in my garage for a decade or two. Installation went smoothly, but when I started the process of level setting, an obvious issue presented itself.

Noise.

Specifically, it's the hissing noise you get from tweeters when you've got your levels set too high on an amplifier. Only I don't believe my levels are set incorrectly. Let me explain.

The only new piece of gear in the car is the Alpine CDE-102 head unit that replaced my dead stock deck. Next down the chain is an Alpine ERA-G320 EQ. The EQ used to be connected to a CDA-7873 via Ai-Net with absolutely no issues whatsoever. Because the new deck lacks Ai-Net, it's connected to the EQ with RCAs (the EQ also has RCA inputs). The front outputs of the EQ are connected to an Alpine MRV-T303 which is driving an a/d/s component set.

After setting the input level on the EQ (EQ volume turned all the way down, CD volume at 28/35) I'm getting a pretty bad hiss from the tweeters. The gains on the amp driving the component set are turned down to minimum (increasing them compounds the problem badly). Any reasonable volume increase produces a baseline hiss that's unacceptable.

So in summary, levels are matched between the head unit and EQ per the EQ's instructions. Gains are all the way down on the amp. Hiss is present.

I've swapped out RCAs. I've checked cable routing. I've checked ground of the EQ. Noise, noise, noise. Remove the EQ from the signal chain (connect head unit directly to amp) and the noise vanishes; It's definitely the EQ.

Any ideas? The one thing here that has me suspicious is the 2v output on the head unit. I've never used the RCA outputs on a deck with a 2v output voltage before, so I'm curious if that could be the culprit. I'm tempted to hunt down a 4v deck and put it in just to see if that remedies the problem. Other than that, I'm out of ideas.

Any help would be appreciated.

Thanks,

Chris

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[maylar 10+ year member]

Could be a noisey transistor or IC in the EQ. It happens to audio electronics sometimes. In the old days we would troubleshoot that by selectively spraying freeze mist on components and listening for the noise to change.

 

[MCShaffer]

Thanks Dave. I suspect that the eq is bad, so I'm going to end up removing it from the system. I was just hoping that I'd be able to retain it, if for no other reason than I spent a ton of time integrating the display into the dash. oh well.

Chris

 

[Tupolev 10+ year member]

Could be a noisey transistor or IC in the EQ. It happens to audio electronics sometimes. In the old days we would troubleshoot that by selectively spraying freeze mist on components and listening for the noise to change.

I did that to a MOBO once, I got the jitters and sprayed a EC cap on accident. It blew up in my face. Got sprayed by some hot sticky liquid. //content.invisioncic.com/y282845/emoticons/blush.gif.99bc659ee2012b7d826165e26fb5eebe.gif

 

[Epic0318 10+ year member]

I did that to a MOBO once, I got the jitters and sprayed a EC cap on accident. It blew up in my face. Got sprayed by some hot sticky liquid. //content.invisioncic.com/y282845/emoticons/blush.gif.99bc659ee2012b7d826165e26fb5eebe.gif

wasn't the first time you got sprayed by some hot sticky liquid:naughty:

 

[akheathen Premium Member]

what eq is it, and where is it grounded?

 

[MCShaffer]

akheathen - The EQ is an Alpine ERA-G320 and it's sharing the ground distribution block with my three amps in the trunk. The four units (EQ plus three amps) are grounded through the block and ultimately grounded at a common point in the trunk that I drilled just behind the rear seats. Total length of the ground wire run is about 3 feet.

Thanks,

Chris

 

[CHEMMINS 10+ year member]

Just run a jumper bypass around the eq and see if the noise goes away.

 

[MCShaffer]

CHEMMINS - I'm not sure what you mean by "jumper bypass". When I bypass the EQ in the signal chain the noise disappears. That's how I identified the EQ as the source of the noise. I'm just trying to figure out if there's anything about the way that I've installed the thing that's introducing the noise. I may try to ground it at a different location just for the Hell of it. I'd really rather not remove the EQ from the system if I can avoid it.

Chris

 

[Tehgregzor 10+ year member]

Could you send it off to be repaired? Or is it a dead brand?