Audio system issue - Crackling at all volumes

[Mick]

I've been trying to chase down an issue with my audio system where there is static/crackling at all volumes. The noise is only in the front channel. The volume of the noise doesn't change when you adjust the volume on the radio, it's at a constant level.

Here's a video of the issue:

https://1drv.ms/v/s!AmfsEZfS1Karsq1v8M9vncGx98SHZg

Things I've tried:

• Sent the head unit into Doctor Don's for a refurbish. He replaced all the caps and said that he bench tested it and it is working fine.
• I pulled the amp and replaced all capacitors and a couple of resistors
• Replaced the amp with used unit that I got from mwagner10702 (Thanks Mark)
• Checked and cleaned the ground under the rear seat
• Took a good look at the wiring behind the head unit, It's not hacked up and looks to be all original.

I emailed Doctor Don, explained where I'm at, and asked for advice. He responded with only 2 words "check speakers." While I don't have a problem doing that it feels like a waste of time, so I'm not sure I want to take his low effort advice. It seems to me that the issue is somewhere in the amplification stage since it doesn't change with volume.

I haven't chased the wiring under the dash. I suppose that's the next step. I've been putting it off because working under the dash is such a PITA. When I do get under there I'll be looking for the any splices a previous owner may have made, and try to find and check the ground.

If I do decide to try swapping out the front speakers, is there an aftermarket speaker that is a direct fit?

Just wondering if anyone has had a similar issue.

--

As an aside. I don't even use the radio, but it it bothers the shit out of me me that it doesn't work.

[ADA///M]

I'd bet on wiring to speakers or speakers themselves. Speakers is an easy check. There's plenty that fit. I believe theyre 5.25" iirc.

I put in some mb quart components, but any decent 5.25 will do.

also, maybe some interference? is it only with the radio?

[Mick]

Thanks, will check them out.
Noise is there whether using the radio or cassette.

[jimmy p.]

Hey Mick,
Not for nothing, since the problem is only with one end of the car have you tried swapping the speaker outputs front to rear to see if the issue moves or stays, that will at least help you narrow down where to look.

Does your car have the Front to rear fader wheel?
That might be an easy place to start.

[Mick]

I did try that and the noise stayed in the front speakers. It happens on both sides left and right, and swapping left to right made no difference. That's what made me think it was in front channel of the amp, but it could also point to speakers. I just can't get past the symptom where the volume of the noise doesn't change as you increase the volume. I would think a bad speaker would get worse as you put more power into it.

My car doesn't have the fader.

[mwagner10702]

Check the wiring to the speakers - you may have an exposed wire that is shorting to the body (probably the insulation has worn through over the years). Check the wiring as it passes through the door and pillar.

The other likelihood is your front speakers could have bad voice coils and need to be replaced.

[mlytle]

Check speakers...

[CamayroZ]

That sounds like electrostatic noise to me. It sounds like you are picking up conducted noise some place.

To understand, you are driving the output of that radio into a separate Amp, and then the Amp is wired to the speakers? FWIW: That radio is capable of running speakers without a separate Amp.

You don't have the speaker wires backwards do you (+/-)? The speakers would still work, but "weaker" and may sound strange. Each of the (-) speaker wires would have a corresponding "black" n it.

I did try that and the noise stayed in the front speakers...

You swapped the speaker wires from front to rear? And the noise stayed on the front speakers? --> That means that it is not the radio/amp output, but rather the wiring between the radio and the front speakers, or the front speakers.


1) Remove the speaker cover for one of the "noisy" front speakers and just run a pair of external test wires from radio to the speaker. Does it go away? If yes, it is the wiring.
1.1) If the noise stays, then it maybe the speaker. Do you have "boom" box, connect the speaker output to the speaker and see what happens.

2) You can easily try grounding the body of the radio and see if it helps?

If you end up buying speakers, make sure that you buy correct impedance.

[Mick]

Thanks for the advice.

Yes, it's the OEM system, radio and with an amp in the trunk.

I don't think I reversed the polarity, the speakers use a common ground. Also the radio connectors are keyed so you can't flip them.

I haven't looked at the speakers yet. It's possible someone reversed the polarity there but they would have to have modified the factory wiring to do it. I'm pretty sure the speakers use 2 different size spade connectors. My car is pretty much unmolested but you never know. Maybe I'll find that someone messed with the speakers at some point.

My next step is to pull the speakers and bench test them. I'll also temporarily wire in a speaker I have kicking around to see if the noise is in the car or the speaker itself.

[CamayroZ]

OK, good luck.

I have the same radio, and no amp. That particular radio, if I remember correctly has dedicated speaker wires (Pair +/-) for each of front and rear speakers. It is a "floating" circuit design to minimize noise. I went through this 2 years ago as I removed the Alpine that I had put in 30 years ago, and replaced everything with a brand new/restored OEM radio.

I can post the wiring diagram for you, but unfortunately this site does not allow posting anything... "Invalid geometry..."

I am not a fan of common speaker grounds, but it happens.

[Mick]

I pulled the head unit and bench tested it with a known good speaker. The noise is definitely being output by the front channel of the head unit itself.

I called Doctor Don. He was puzzled by how he could have missed it but was apologetic and was happy to take it back to have another look. I'll update in a few weeks when I have it back again.

[jimmy p.]

I pulled the head unit and bench tested it with a known good speaker. The noise is definitely being output by the front channel of the head unit itself.

I called Doctor Don. He was puzzled by how he could have missed it but was apologetic and was happy to take it back to have another look. I'll update in a few weeks when I have it back again.

Thats great news that he will stand behind it.
I need to send him a couple head units. Mine all crackle and I'm so bored with cleaning the pots every season as a band aid LOL.

I know hindsight is 20/20 but in my day job noise situations are almost never the speaker, its almost always somewhere in the signal chain.
The speaker (be it ever so important) is just a dumb magnet. Its almost always just reproducing what we put into it.

[Reelizmpro]

As Jimmy stated, I was going to suggest cleaning the volume potentiometer with something like WD40 or contact cleaner. It has worked for me in the past as an easy fix on 2 head units.

"As potentiometers age, oxides can form on the metallic contacts of the wiper or slip ring and contaminants can gather between the wiper and the resistive track. Debris causes the potentiometer's signal to “jitter” and emit a crackling noise in audio circuits."

[Mick]

Got the radio back from Dr Don and it's working great. Turns out there was a bad component in the front output stage that he had missed.
Thanks for all the advice.