Jonasand

Have a E61 lci with hifi and was gonna replace the amp.

Took signal from org wires and spliced to rca.
Used output Wires to speaker to amp.

Hooked it up to a separate battery and all playef nicely.

So went on and Installed all in car with a grund from a bolt in chassi and 12v directly to battery with fuse. Used the 12v outlet in trunk as remote.

Everything started and have a constant distorsion.. A interferance.

Tried giving power from battery with remote, used other cables, even Hooked all up straight to battery.

Nothing works.

But if i connect to a separate battery all is good.

What am im missing?

And no the plug is not connected to the old amp

Jonasand

Dont know If distorsion is The right word but it is a constant humming, even if all is off in car and I keep amp on and open the door the speaker pops and start humming...

I even tried using the positive, negativ and remote from the org harness to no sucess.. But if hooked up to a sepratae batter all is good.

The splicing is correct, messured everything.

Jonasand

If I hook up the separate battery it works as said. If I then take a ground anywhere on the car and attach that.. The humm is back.

Cant measure any volt that isnt supposed to be there.. And if it was my splicing rca etc... Why does it not sound When on separate battery?

habbyguy

There could be a ground loop. Double-check your ground connection, and I'd suggest measuring the voltage at the amp. If there's a flaky connection on the signal path's ground, you could get a ground loop as it has to "reach back" to the chassis ground instead of using the one by the signal wires.

You might try paralleling in a large filter capacitor on the main power line - that can fix a host of issues if the problem happens to be electronic noise on the power line (the cars have an awful lot of electronics, after all).

Jonasand

Well i checked so many the Voltage, its at what it should. Messured the earth point that is attached to the amp to - car battery.. No current and good ohm.


Ive tried diffrent cables, diffrent location "chassi in trunk, the one under the hood and the battery"

Everything i tried works Great if i use a separate battery.

Finally i took a rca to 3.5mm wire and hooked up to amp and the to my laptop and used the cars power to se what happens then.

Lord and behold all quiet and speakers play, with the cars battery on +- and remote.

Im no techincal gurue.. But why does it Work if use a external source with other rca and cars power.
And the other way around When using separate power, but cars signals.

Im baffled, never had so much problem installing a amp... But on the other hand i noticed that bmw in general always puts up a fight 🤣

donpb

Voltage readings do not show noise. You'd need an o'scope for that. To filter out noise, try what @habbyguy suggested to install a filter capacitor.

Jonasand

Gonna look into that.

In the meantime, how come it works with the little oem amp and not the big one with the same wires?

Why is it working if i use signal from car but a externa battery.

And if i use power from car but use another source as signal as my laptop, it works aswell.

donpb

Because your source is not sharing the same GND.

Your new Amp may not have noise isolation to something in the car, so you may have to jury rig your own filter.

Jonasand

Well the idea about the ground i had the same idea aswell, but since i tried the negativ terminal on battery, the one under the hood and chassi.. Shouldnt the other one aswell go to chassi?

What do you mean with jury rig? Im Swedish and some few words are not in my head 🫣

If I bought a loc rca with filter should that Work, was thinking on trying the trick where you wire the terminal on rca on amp to the ground to the amp?

Aswell make ohm reading on good ground.

In really trying to get in my head what you guys are saying, but as said.. Some words/explain om lost at understanding.

And the ground, if its not sharing the same.. Why does the org wires work with org amp.. But not with the other amp?

Could this work?
Couldnt find it in english

Ive seen many grounding the headunit, but thats alot of work taking out the original ccc.

Not trying to be ride or dumb.. Just hard understanding some parts.

As why the same wires work with org amp but not the new, as why it work with external power source or signal.

donpb

Jury rig means to figure out your own filter. There is possibly a GND loop, and your laptop probably works because its GND is out of the loop (isolated).