Strange stereo issue - interference but not the usual kind

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Topic author
Ultimatequinoxe
Posts: 27
Joined: 12/03/14 19:44
Years of MR2 Ownership: 4
MR2's Owned: 4
Gender: Male

Strange stereo issue - interference but not the usual kind

Post by Ultimatequinoxe »

Hi all, I hope everyone is safe and sane.

I'm having a head scratch and likely moving onto the factory amps as potential reasons for a strange interference/noise issue I am having, on my untouched UK MK2 Rev3 (bar the stereo). Two different issues with two different head units, which I will explain in short first, and add a long version after for those more bored :D

Old head unit has no top end sound all the sudden, low frequency only. New head unit has all frequencies but a hell of a lot of interference noises. Amp wiring issue or failure suspected. All of this is without the ignition on or engine running, key to ACC only.

Longer version in more detail...

I have no additional amps, factory pap only. No ground loop isolators or anything fancy added on, head unit untouched since I bought the car and all was fine until recently. It had an older Pioneer run of the mill head unit sat above the factory CD player (not wired up) which was running fine through the factory sub and both side speaker sets.

All I've done since the last time I used the stereo was swap the exhaust downpipe (if anyones got a good spare by the way, let me know, the new one I got is awful and needs returning), I took the battery off to charge it whilst sat for many days during lockdown in the garage, and I swapped the disintegrated factory sub speaker behind the passenger seat for another same sized (and ohm'ed) speaker.

Since then, when running the pioneer, I only get very low frequency sounds. So I thought, maybe the head units packed up internally, being rather old. So I bought a cheap chinese touchscreen thing to test with, and that has bass and treble fine, but a lot of interference noise - change anything on the screen, the annoying cycling led lights on the side etc all make slight changes to the noise (the pitch alters in the high end frequency noise alongside the slight buzzing noise as well).

There is a fair amount of pop and discharge sound when turning the ACC to 'off' as well, when a head unit is plugged in (even when bypassing straight to the battery). The noise is even heard without the RCA's to the speakers plugged in, but with them plugged into the head unit, the noise is amplified through all speakers. Its not mega loud, but very clearly heard and not comfortable.

Running both stereo's indoors and they are both fine. I've run a ground off a factory earthing point on the car and no change to either stereo, and run a fused wire straight off the positive terminal on the battery, and no change. Makes me think its something in the amp area of things. I have checked the alternator for any chance of hitting something when swapping exhausts and removed the sub entirely and checked the wiring harness behind the head unit (as said, it was all fine and not touched until after the issue showed up).

Anyone encountered this before on their MR2's I wonder? Anything I've missed or experiments to try for eliminating possible culprits?

Many thanks! :)


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