Speaker whine, bad ground?

[Xarano]

Hi All

Ever since installing my aftermarket headunit, I always get a high pitched whine from the speakers right after turning the car on.
This will persist for a few minutes or so until it suddenly goes away. However sometimes I will hear it while driving too.

After searching around it seems like it would be caused by a bad ground or interference somewhere between the headunit and the Bose amp, some people suggesting using a ground loop isolator to fix. However I would like to find out if this is fixable without any additional purchases!

For context, My headunit is an Atoto unit with 4 RCA preouts, which are plugged into the PAC MZ11 cable harness RCA plugs before ultimately going into the car via the connector in the dash.
As far as I can tell, ive not grounded the headunit or the harness/cables in any way, just plugged everything in as instructed.

Side note: when I plugged everything in, I noticed the stick headunit has an extra connector on the back which has nowhere to go on the new kit, anyone know what it does?

[Leck3000]

I have a high pitched noise since changing mine to an aftermarket as well. Would also like to know a reasonable fix for this. By the time I have music playing it is no longer noticeable but annoying all the same knowing it isn't quite correct.

I also get a pop from the speakers every time I turn the car off, about 10-15s after switching off and removing the key, any suggestions for that at the same time?

[Xarano]

The whine is probably be coming from the alternator, and relates to how hard it's working re-charging the battery.

This would be why it is most noticeable just after starting, as the battery voltage will be recovering from starting current.

You can check this by ensuring that battery is absolutely fully charged before starting, and the noise should stop much quicker.

The aftermarket unit might be particularly sensitive and need a suppressor fitted close to it's power input,
something like this https://www.ebay.co.uk/itm/353083115032

It's possible that a loose/dirty/corroded connection, either size of the battery, is making the charging system work harder, in which case finding and sorting the connection would make a big difference.

Regarding the "pop" that's the internal power supply capacitors, designed to smooth the incoming voltage, discharging below a threshold after the power is removed. As such it's not a "fault" it's a "feature" - people used to pay extra for systems that do that.

[Xarano]

Thanks Warp,

Very helpful info.
The pitch of the whine changes directly with the RPM of the engine, guessing it's caused by how much or how little work the alternator is doing?

Ill purchase one of those suppressor thingies, how do I attach it to the headunit, just with a screw or?

[Leck3000]

Yes mine certainly changes pitch according to revs, will look to get one of those as well perhaps but not looking forward to fighting with all the cables again to make it fit back in place.

Understood on the pop, never mind, would have rather cured that than the whine but they are insignificant troubles in the grand scheme of things.

[warpc0il]

The alternator revs are directly proportional to the engine revs, which would affect the pitch.
The load on the alternator would impact the relative volume.

You could try fitting the suppressor on the output of the alternator, which is much easier to access, but is sometimes less successful.

[Lemon]

the whine you are hearing is due to a ground loop, check to see what grounds there are for the head unit as it is probably grounded differently to the OE unit.

[rcordran]

For info - I had a similar issue when using the Aux in input in the armrest on my R3. Fitted a PAC SN1 Ground Loop Noise Isolator, and that solved the problem. That has a 3.5mm plug and socket so goes inline. It won't help with your problem, but might help someone else. For me, the whine increased with the RPM.

[Lemon]

For info - I had a similar issue when using the Aux in input in the armrest on my R3. Fitted a PAC SN1 Ground Loop Noise Isolator, and that solved the problem. That has a 3.5mm plug and socket so goes inline. It won't help with your problem, but might help someone else. For me, the whine increased with the RPM.

Thats because the grounds for the audio system have created a circuit and are picking up the noise from the alternator, i'm wondering if the OE head unit is isolated from the units chassis and grounded through the harness...

https://help.campbellsci.com/CR1000X/Co ... -loops.htm

https://www.lifewire.com/whining-noise- ... put-534592

[sKenDread]

Ground loops can be a cause but also dirty power can too.
There are a few ideas to check but basic rules first.

• Power supply and earth should be of the same gauge ( even if the headunit chassis is grounded )

I would be inclined to ask for more details? An isolator should be a last resort really. The underlying issue is still there

• Where does the source of power and (if any) ignition come from?

• Are you still using the OEM amplifiers

• Are you using aftermarket amps?

Hope you get it sorted
Keni