Audio/Electrical Experts, Help Me Keep My Sanity...

[Brando]

Okay, I've got this nasty, nasty buzzing noise (constant frequency, does not change with RPMs) from the front-right speaker. This is literally driving me nuts and I've had to replace the equipment once so far...

Here's the setup:

4-channel amp and Sub Woofer amps in the front trunk. Both are fed power and ground directly from the battery via an autoblock. I'm using the pre-amp output RCA connectors from my stereo to the amps.

The noise started about a month or so ago, very faint on both front speakers. I asked a local audio shop what to get to fix the noise and they suggested a ground-loop isolator. I bought one, followed the directions and hooked it up. Cranked the car over, the noise sounded literally like a saw going off in the cab, a loud pop, then more high-pitched whine. Then no sound. Great.

I figured something was wrong with the isolator internally... Bench-tested the 4-channel amp, it's toast. Bench-tested the stereo, toast as well. Front speakers were shot too. Sounded like it shotgunned the audio equipment.

Went back to the audio shop, explained what happened. They agreed, sounds like the isolator was shorted internally and took the equipment with it. They gave me 50% off for some speakers and a replacement amp. I picked up a new stereo at Fry's as well.

Hooked it all back up last night, still getting the original, faint buzzing noise. I spent some looking online today at lunch and the recommended fix i found was to put a diode on the Ignition +12v to the stereo. Put that in as well, still the faint buzzing (no change). Time to bust out the multi-meter as something must be grounding out...

I test the speaker line for the left, no grounding issues. I check the right... getting a few ohms across the + and - speaker wires. Yup, something's grounded out. Traced it back to the factory harness for the right speaker is grounding somewhere. I pulled the passenger blower motor cover, disconnected the door speaker harness and ran a new line to it.

STILL getting this incessant buzzing. It's just on the front-right speaker.

[X] New Stereo
[X] New Amp
[X] New RCA wires
[X] New Speaker Line
[X] Same Problem

I'm literally going insane over this. It may help to mention that this buzzing noise only comes on when the ignition is in the "run" position and when cranking (it's real bad then). I've got an MSD ignition as well, if that matters. Any and all help is much appreciated.

[T77911S]

i like the car status you have. i need one of those at my door so i(we) know what is drivable when i go out the door, actually, what is not drivable.

it works fine with the engine off?

i was thinking maybe the alternator. bad diode, but if you put one in line that should have fixed/helped it, but it would not hurt to go ahead and check power.

you may contact MSD and see if they have had problems related to their boxes

[kiwiokie]

Did you run new speaker cable from the amp all the way to the door speakers?

[gshase]

Aircraft Spruce sells several caps and noise filters for engine noise, worked for my airplane radio.

[Brando]

T77911S, I'll have to call Mallory and see what they say about it.

kiwiokie, I did run new cables from the amps to the door speakers. Issue still persists.

ghase, i'll have to find out what the caps may do... I already tried noise filters and they don't work.

[Gogar]

1. Stop buying stuff and throwing it at the stereo until you do a few things.

2. Flip the speaker outs on the amp left to right. Does the problem move? then NO, the problem is a speaker or speaker cable. If YES, then the problem is before the speakers/speaker cables.

3. Since you're using RCAs, flip flop the RCA inputs to the amp and see if the problem moves. If it does, then YES the problem is before the amp, in the head unit or RCA cables.

4. Does the buzzing noise happen with all the input cables unplugged from the amp?

5. If you have some kind of random "home" bookshelf speaker or something, take it out to the garage and run one side of the amp to it. Does the buzz happen? If NO then there's some kind of grounding problem with your speakers in the car or speaker cables, as you mentioned.

[kiwiokie]

I think this post was the wrong way around, if the buzzing moves it is a problem before the speakers/cables, if it is still in the right hand door speaker then it is a speaker/cable issue.

"2. Flip the speaker outs on the amp left to right. Does the problem move? then YES, the problem is a speaker or speaker cable. If NO, then the problem is before the speakers/speaker cables."

[Brando]

I'll try swapping some connections when I get home and see if that changes where the buzzing goes...

[Gogar]

kiwiokie you're right, I edited my post.

[Brando]

Thank you guys... I will follow the steps in that thread to find where the issue really lies. Just the walkthrough I was looking for.

[dshepp806]

ignition noise.

Doyle

[86 911 Targa]

Originally Posted by Brando

Thank you guys... I will follow the steps in that thread to find where the issue really lies. Just the walkthrough I was looking for.

Brando,

Have you tried connecting your speakers directly to the radio?

This would by-pass the amp.

What is the voltage output of your alternator?

It should not exceed 13.5-14.0 volts at 2K rpm's.

You may pm me as needed.

Good luck,

Gerry

[dshepp806]

+1 on bypassing the amp, if you can. This will certainly eliminate a box.

Doyle