What's the best way to resolve my headphone hum noise

[generalizedidentity]

Hi,

I'm using my headphone with my laptop through wired connection, and my headphone makes hum noise whenever I'm in the following situation:

The picture is a bit simplified because actually I have two outlets. However, even if I connect my laptop into one outlet and my electric pad into the other, I can hear the same noise.

Conversely, I don't have hum noise if I don't touch any device using ungrounded plug while I'm wearing my headphone.

Moreover, I also don't have hum noise if the grounded plug is disconnected from the laptop while I'm using any ungrounded device.

In this context, I'm finding what's the best way to deal with this hum noise. For instance, I'm wondering if using an usb dac (e.g. Sonata HD Pro?) between me and the headphone could reduce the noise, or I'm also wondering if I should buy a 3.5mm isolate in order to deal with the case. Thank you for reading and please let me know if you have any thoughts!

 

[AdamG]

Is your iPad or phone plugged into same electrical socket/circuit as the laptop charger?

 

[generalizedidentity]

Is your iPad or phone plugged into same electrical socket/circuit as the laptop charger?

Yes, my studio has only one socket with two outlets!

 

[AdamG]

Yes, my studio has only one socket with two outlets!

It sounds like your basic ground loop hum issue. If you unplug the iPhone or iPad while touching does it go away?

If yes, then just get a ground drop cheater plug for use on the IPhone/iPad plug in site.

Google “Cheater plug adapter”. This should fix the hum ground loop.

 

[Lambda]

“Cheater plug adapter”. This should fix the hum ground loop.

Not sure if this is save advice to give to someone unfamiliar with the involved risks
http://web.mit.edu/jhawk/tmp/p/EST016_Ground_Loops_handout.pdf

generalizedidentity Pleases read page 6-8 before Attempting to do so

A simple and cheap usb dac might be a better fix. maybe the apple usb dongle is alredy better as the laptops internal DAC.
if a usb dac alone is not helping, a usb isolator should fix it for good (and save)

BTW: To me it sounds like the laptop is not properly grounded.

 

[AdamG]

It’s just low voltage DC iPhone/iPad charger involved. I am aware of how lifting the ground can be dangerous. Why I specifically said use it for the phone/iPad charger.

 

[Lambda]

It’s just low voltage

until a capacitor or the transformer fails.

Why I specifically said use it for the phone/iPad charger.

Do they even have an ground?

 

[Lambda]

This would likely solve it:

And what would you plug into this?

 

[Zensō]

And what would you plug into this?

Sorry, this is actually the one you’d want for your setup:

https://www.fullcompass.com/prod/066358-ebtech-hum-x-hum-eliminator-ebtech

 

[dmac6419]

until a capacitor or the transformer fails.


Do they even have an ground?

remove the screw from wall plate and screw it into the round hole and you should be ok,save $75

 

[Lambda]

acbarn
80$ for a ground lift...

Maybe should not assume everyone is from the land of the 2 phase 60Hz AC with NEMA 5-15P plugs ?

 

[Zensō]

acbarn
80$ for a ground lift...

Maybe should not assume everyone is from the land of the 2 phase 60Hz AC with NEMA 5-15P plugs ?

Yeah, well this one works and won’t electrocute you. If there’s something cheaper that does the job safely, please report back here.

 

[Lambda]

well this one works

Only for the special Case of low impedance and and low voltage Loops with NEMA 5-15P plugs
Where do you assume a loop like this in the Schematic OP provided.

 

[AnalogSteph]

OP, what are your headphones?

It seems to me that mains leakage from the Y capacitor(s) of the ungrounded device is traveling through you and the headphones towards earth.

This is sort of the reverse of something I found at one point - a Soundmagic E10 in-ear would hum when plugged into something powered by a floating power supply, whether it be an MP3 player on a USB charger or a laptop with a supply sporting a 2-prong power cord. I chalked it up to insulation just not being very good, I mean, how good could an in-ear really be in this respect? Highish sensitivity (about 125 dB/V @ 16 ohms) isn't helping.

I'm afraid there's not very much you can do about this except provide earthing for the offending floating devices somehow (probably doesn't even need to be super low impedance). Turning the plug around (if possible - requires non-polarized mains plugs) might help for some.

Hmm, when I look up "electric pad" I get electric heating pads. Should be a fairly simple device, and I wouldn't normally assume the heating element to have much capacitive coupling to you through the pad, but I might be wrong. Is the thing certified in terms of electrical safety (UL, CSA, TÜV GS or equivalent)?