Squeal over radio. Need audiophile help (Page 3/3)
Patrick AUG 07, 06:06 PM

quote
Originally posted by RCR:

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.
Mike in Sydney AUG 07, 08:08 PM
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.)
Mike in Sydney AUG 09, 02:11 AM


quote
Originally posted by Mike in Sydney:

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).]

RCR AUG 09, 09:13 AM

quote
Originally posted by Mike in Sydney:



This is the picture of the RF Shielding that I mentioned. The shield is circled in red. The jumper is circled in yellow.




Thanx Mike and thanx for the pic. I do know what it is, it's just a little more difficult to install on my car.


It also squeals without the ignition operating, so it's not noise from the back.
RCR AUG 09, 09:30 AM
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).





Bob
RCR AUG 09, 10:17 AM
Take two.

(I think I'm posting to vent).

- 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)



Bob
Spadesluck AUG 10, 05:51 PM
My take on it, you are making progress! 🫡

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
Patrick AUG 10, 06:34 PM

quote
Originally posted by RCR:

- 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.
RCR AUG 13, 08:36 AM
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.

thanx for the support..

Bob