buzzing sound from external speakers whenthe laptop is turned off

My current model : Hansung BossMonster EX74 LV70IE (Clevo P770ZM)
My OS : WIndows 10 pro (genuine product)
My hardware :
GTX980m
Intel xeon 1231v3
HyperX 2133mhz ddr3l ram 16gb
500gb m.2 ssd + 3 TB HDD
ac7265

Questions : Ok, as you can tell from the name of thread, my external speaker, Creative T40 II, makes odd buzzing noise, that is close to the electronic poping sound, when the laptop is turned off. It is especially noticable when I am charging my laptop, which means I can still hear it when laptop is not charging as well.

First I thought it was a speaker's problem, I replaced the speaker to the new one, but the problem did not stop. Than, I thought it was a software problem, so I re-installed the windows 10, but it did not help. As far as I guess, I am pretty sure that it is not problem of ground connection because I've used this speaker to 4 different laptop, and only my laptop had a problem.

Which means, my laptop is having a problem, but I can't really tell "what" is causing this problem. Because, when I turn of the laptop, and use the headphone, I can not hear any buzzing sound, it only happens to external speakers. The only reason of this situation that I am guessing is that once, I've changed the power cord of my laptop with my monitor, since my laptop has Europe powercord layout, while the monitor have US standard layout. It was fine for few days, but later on, the monitor kinda broke and the laptop was starting to make buzzing noise. I've changed the power cable back, and my monitor is fine now, but the laptop is still making buzzing noise through external speaker. Can anyone help me?

 

It really does have all the symptoms of a ground loop issue ...

Unlike almost very other laptop, the ZM's large, 330W adapter is unshielded, meaning it needs a grounded cable and socket. If the other four laptops used shielded (two-prong) adapters the that'd explain the absence of noise with those.

Aside from the laptop's, also check the adapter of the speakers themselves; the sticker should have a logo resembling a double rectangle to indicate it's shielded and, hence, does not require a grounded cable+socket.

And, if present, check if disconnecting the ethernet cable helps. That thing is powered and since the router it originates from is likely on a different circuit it is a common cause of ground loop. And, of course, check if running on battery solves the issue. Preferably you want a 'clean', isolated laptop with nothing connected, except the audio cable to the speakers. Next, remove the battery and run on the, properly grounded, adapter only. Ah, and try a different socket, too, on the other end of the house or even somewhere else.

Failing everything, then yes, there's always a degree of electric noise with every device, so it could really be the laptop itself. If so, consider an impendance plug. These work perfectly, whether the issue is ground loop or merely electrical noise. Only drawback is that maximum volume will be lower.

 

I am currently using 230w adapter, since my xeon 1231v3 is not overclockable. My four different laptop used three prong and two prong. (MSI GT70, three prong, Aorus x3 plus, Europe standard power cable with converter). My speaker is using two prong, and ZM is currently using converter for US ( http://i.ebayimg.com/images/g/ZgwAAOxyYYlRqiJa/s-l300.jpg currently using this one). The reason why I think it is not ground loop is because this it worked just fine when I came to the US, and for 3 ~ 4 days. Also, I can still hear buzzing sound when the laptop is unplugged.

 

Try using a DAC/AMP. It eliminates all interferences an makes sound quality better.

Sent from my D5803 using Tapatalk

 

That's one alternative. They're geared more towards audiophiles/enthusiasts/professionals, but there's no doubt that they provide better quality audio than what's integrated.

 

I do have amplifier, but it is for my headphone, not my speaker.