I've been working on the interior and wanted to install the stereo system so I can button up the dash and side panels.
I have a Boss head unit, with Boss 4 channel amp. Kicker 5.25 speakers in back, with JBL 6.5 components up front.
When I place the key in accy, I get a faint buzz on the speakers, not too bad. When I place the key in run, I get an annoying high pitched squeal. When I start the car, it's not tolerable.
The battery is mounted in the frunk.
I've run seperate power and ground from the head unit to the battery. I have a short run from amp to battery, direct. I tried grounding the case of the amp because it's mounted on the plastic floor of the frunk. I bought new Gearit RCA harnesses, no luck.
I've been working on the interior and wanted to install the stereo system so I can button up the dash and side panels.
I have a Boss head unit, with Boss 4 channel amp. Kicker 5.25 speakers in back, with JBL 6.5 components up front.
When I place the key in accy, I get a faint buzz on the speakers, not too bad. When I place the key in run, I get an annoying high pitched squeal. When I start the car, it's not tolerable.
The battery is mounted in the frunk.
I've run seperate power and ground from the head unit to the battery. I have a short run from amp to battery, direct. I tried grounding the case of the amp because it's mounted on the plastic floor of the frunk. I bought new Gearit RCA harnesses, no luck.
Not sure what else to look at or what to do.
Any audiophiles that can help???
thanx
Bob
Sounds like a poor ground or line noise. Do you run your RCA / Speaker wire along your power and ground? Try and change your ground / if that doesnt work you can wrap your power and ground with foil to see if it goes away.
They also make some filters you can add in on the RCA's but its more of a band aid to the problem.
This may or may not be related... but years ago I started to get some kind of interference noise on my Fiero's radio that went up and down in frequency with the revs of the engine. (Found the thread Here.) Shortly thereafter, the alternator failed (stopped charging). Replaced the alternator... racket on the radio was gone.
It occurred to me that when I first hooked everything up, I had a bad connection at the battery that ultimately roached my first amp ( I'm running a replacement). Any chance the head unit was damaged, causing this noise issue?
Sounds like a poor ground or line noise. Do you run your RCA / Speaker wire along your power and ground? Try and change your ground / if that doesnt work you can wrap your power and ground with foil to see if it goes away.
They also make some filters you can add in on the RCA's but its more of a band aid to the problem.
I've run separate power and ground from the head unit to the battery. I have a short run from amp to battery, direct. Any chance the head unit was damaged, causing this noise issue?
To me, test the head unit on the bench; if it is good, then make sure the speaker/amp lines are separated from any power source.
------------------ Original Owner of a Silver '88 GT Under 'Production Refurbishment' @ 136k Miles
When I tested my head unit, 5 channel amp, speakers and sub on the bench everything was great. When I put it in the car it had a feeback type sound. It ended up being a ground loop issue.
On my amp, I had a choice of line level or RCA inputs, and I used the line level as that is what my head unit had. The instructions said that the line level input connectors (3) were to be gounded at the same location as the amp ground so that is what I did. As I was troubleshooting the issue, I disconnected the line level input grounds and the noise stopped and everything worked great.
So I would check any additional grounds the instructions might have suggested, especially on the input to the amp, and start disconnecting them.
Prior to finding the ground issue, I went down the rabbit hole for signal conditioners, locations and routing of power wires vs. speaker wires, and none of that helped.
I've run separate power and ground from the head unit to the battery. I have a short run from amp to battery, direct.
So, a "separate power" circuit means it is hot at all times AND that the music system is still being feed "On/Off" from the Ignition Key and the Radio Fuse, yes?
[This message has been edited by Vintage-Nut (edited 07-02-2025).]
So, a "separate power" circuit means it is hot at all times AND that the music system is still being feed "On/Off" from the Ignition Key and the Radio Fuse, yes?
I connected the Battery direct, first, then tied ignition to it so it had power all of the time. No bingo...
When I tested my head unit, 5 channel amp, speakers and sub on the bench everything was great. When I put it in the car it had a feeback type sound. It ended up being a ground loop issue.
On my amp, I had a choice of line level or RCA inputs, and I used the line level as that is what my head unit had. The instructions said that the line level input connectors (3) were to be gounded at the same location as the amp ground so that is what I did. As I was troubleshooting the issue, I disconnected the line level input grounds and the noise stopped and everything worked great.
So I would check any additional grounds the instructions might have suggested, especially on the input to the amp, and start disconnecting them.
Prior to finding the ground issue, I went down the rabbit hole for signal conditioners, locations and routing of power wires vs. speaker wires, and none of that helped.
Thanx for feedback...
The only grounds connected are the amp ground and head unit ground. I disconnected the GPS antenna, and car antenna just in case.
22 dollar chinese unit works great, Boss units squeal. WTF??
I'm probably going to tear whole thing out and build it on the bench and prove where the issue is. Not sure what else to do, short of put the chinese unit in.
What kind of quality RCA cables are you using? Are they shielded? Are they running next to your power feed? You are definitely experiencing electric interference, sometimes it is not easy to track down as you are finding out.
What kind of quality RCA cables are you using? Are they shielded? Are they running next to your power feed? You are definitely experiencing electric interference, sometimes it is not easy to track down as you are finding out.
Something is wrong, that's for sure. I think the RCAs are Amazon brand, highly rated. They are shielded. The power feed to the amp is direct, battery right next to it. The head unit gets it's power through the stock radio feed. The RCAs and speaker lines come though a hole I made in the firewall.
A new head unit (#3 for different issue) will be here later in the week. It will be bench tested prior to going back in.
I remember chasing down some noise in my system a long time ago. If I remember correctly, it came down to doing a better ground. The problem is the noise can come from multiple places so it can be a challenge to find.
I remember chasing down some noise in my system a long time ago. If I remember correctly, it came down to doing a better ground. The problem is the noise can come from multiple places so it can be a challenge to find.
Once I test the new head unit on the bench, I think I will run the radio ignition wire direct to the battery, then pull fuses attached to the "ignition run" ckt to see what happens. Maybe try to narrow down on which circuit has the ground issue.
Right now it's a guessing game, so I need to narrow the options.
Recently, my radio began to squeal while the engine was running. (It’s a GM Monsoon radio from a 1994 Pontiac Grand Prix. No external amp and no premium sound base reflex speaker.). The squeal would get louder as the RPMs increased and would quieten when the RPMs dropped. While chasing the problem, I noticed the wire connecting the metal shield in the trunk lid over the engine was broken. When I repaired the wire, the squealing went away. I’m not saying this is your problem but it may be worth a look.
Recently, my radio began to squeal while the engine was running. (It’s a GM Monsoon radio from a 1994 Pontiac Grand Prix. No external amp and no premium sound base reflex speaker.). The squeal would get louder as the RPMs increased and would quieten when the RPMs dropped. While chasing the problem, I noticed the wire connecting the metal shield in the trunk lid over the engine was broken. When I repaired the wire, the squealing went away. I’m not saying this is your problem but it may be worth a look.
Hmm?? Thanx for the feedback. Curious, because I do not have a shield. Hope that's not it, because in my application, there is no place for one.
I do not have a shield. Hope that's not it, because in my application, there is no place for one.
I think Mike is onto something.
Most of us don't follow who's done what to their Fieros, and you appear to have one (I looked it up) with a heavily modified body. Your decklid is not factory, which explains why you have no shield. Pontiac put a shield in the OEM decklid for a reason... to cut down on RFI noise. You may need to explore other options.
I think making a shield would be simple. It appears to be just a 1mm steel plate coving the engine bay. The wire is small gauge and appears to be grounded to the frame through the left hinge. (I’ll confirm that this afternoon.)
I think making a shield would be simple. It appears to be just a 1mm steel plate coving the engine bay. The wire is small gauge and appears to be grounded to the frame through the left hinge. (I’ll confirm that this afternoon.)
This is the picture of the RF Shielding that I mentioned. The shield is circled in red. The jumper is circled in yellow.
[This message has been edited by Mike in Sydney (edited 08-09-2025).]
It's been a frustrating morning so far. - Entire wired system in intended location makes noise in Run (engine off) - Used oscope and looked at batt and ign lines at radio. They have some noise on the lines (issue?) - Ran separate power to battery. No noise on lines as viewed with scope. Still has squeal. (not radio power?) - Rigged separate amp (amp2) in car on passenger seat. Same radio connections. Different RCAs to amp2. Direct power to batt. No noise. (progress?) - Connected amp1 back up. Ran amp2 RCAs (outside of car) to amp1. Still makes noise. (RCAs not problem?) (when I say "outside". I literally mean outside, thru the window to the front. - Disconnected Remote connection from amp2 and connected to amp1, outside of car. Still makes noise. (Not remote?) - Disconnected speaker wire from amp1 and connected direct, outside of car. Still makes noise (Not speaker wires?) - Disconnected battery feed to amp1. Using amp2 feed, outside of car, connected to amp1. Still makes noise (Not batt feed?) (note I did batt and ground weeks ago).
Probably the only thing I have not tried is pulling all of the wiring from the front and sitting the amp on the passenger seat (like amp2).
- Swapped grounds to amp1 for kicks. No change. - Since I had just about everything disconnected, I pulled amp1 and set it up on passenger seat like amp2. STILL MAKES NOISE!!! - Pull all the extra wiring out and put amp2 up front, using all amp1's original wiring. WORKS FINE!!! WTF???
Now recall, I put a 20$ head unit in, using amp1 and all of the existing wiring, and everything worked. I don't get it...
All I know for certain is that the Boss head unit is not working with the Boss amplifier, but works fine with my 25 year old Kenwood. (Too bad the Kenwood doesn't fit)
But, it made noise with the motor off? Thats definitely not correct, like you may have found out. The amp and radio together might be making for a bad combo. Crazy
- Entire wired system in intended location makes noise in Run (engine off)
Well, that indicates then that it's not RFI that's causing the squeal... so I believe this rules out the lack of a shield in your custom decklid as the source of this issue. Probably also rules out the alternator.
I'd really like to know the cause of this, but I'm done fighting. I squeezed the Kenwood unit in place of the Boss. It's a tight fit and I still need to make a mounting board that uses the Boss holes (don't really want anymore holes in the frunk). Even though the Kenwood amp is a little beat up from age, it sounds great. I'll have to get some pics to close this out.
