Humming noise in USB headset due to ground loop

[ThinkSFO]

Hi,

I encountered an issue that I never thought would happen. I am a regular user of online conference call tool, Webex. I bought a new Logitech H530 USB headset with the thought of a better sound quality for my calls. However, as I plugged it in, it gave a strange result.

The plug-&-play part was just fine. All the drivers were installed and I updated them to the latest version etc. I made sure the new headset has been set as the "default" playback and recording device. But, when I talk to people, they tell me that they hear a low humming noise in the background, like an old fridge. When I set the playback to my own headset, I could hear it too.
After some research, talking to Logitech Tech Support (who were hopeless), I discovered that it is caused due to ground loop interference from the charger (either standard charger or base station).
When I unplugged my laptop, the headset was finally all quiet and crystal clear.

Since, I can be on serveral calls back to back, my laptop battery can't last that long. Does anyone know a better way of eliminating this humming noise issue? I've seen sales of "Ground Loop Eliminator" devices, but they are for speakers. Anyone else has this problem or is it just this laptop?

I'm using a 2 months old IBM Thinkpad T410 running Windows 7.
Headset: Logitech H530 USB


Thanks.

[RealBlackStuff]

Look for an AC-adapter with grounded 3-prong wiring.
Most European varieties have 3-prong, as compared to North-American 2-prong.
The part numbers should be in the HMM.
If you have a 65W now, you might as well look for the 90W version.

Have you tried the other USB ports?

[ThinkSFO]

Hi RBS,

Thanks for that suggestion about the 3 prong AC adapter. I will need to look for one.

I just looked at my Lenovo AC adaptor. It does say that it is a "90W 20V" (P/N 42T4426) adaptor. It's a "135W 20V" on the base station charger (P/N 45N0054).

As for the question about whether I tried other USB ports. Yes, I did. I tried all of them (4 of them on the laptop and 3 of them on the base station) and all gave the same result.
I was hoping that there's another way then go and get a new plug.

I figured that given the T4X series is one of the more popular business laptop, there must be hundreds of thousands of people who use Webex, Skype and other similar web chat tools via a USB or wireless headset. Did everyone go out and get a new 3 prong plug or has someone figured out a better way? Is IBM/Lenovo plan to do something about this?

[ajkula66]

Non-grounded (2-prong) laptop adapter cords have been an industry standard for about a decade in the U.S...at least.

Nothing to do with Lenovo per se, really.

I'm not a Lenovo employee but will say that I highly doubt that they'll address the issue at hand.

Properly grounded wall outlet should minimize this type of interference as well.

Good luck.

[RealBlackStuff]

Have you considered that you could have lemon headphones?
Logitech is not what it used to be...

[poshgeordie]

Test the lack of ground issue by touching a metal part on the laptop and see if the hum disappears - you won't get a shock.

If this works, an easy(ish) way to permanently do this is to bare both ends of a piece of wire and attach one end to one of the External VGA connector hexagonal posts and to hold the other in your hand. What you're doing is providing a very high (safe) resistance (impedance ) conduction path to earth for all the interference signals generated by the AC adapter.
Don't connect the wire directly to a mains earth connection since this could damage the laptop / AC adapter.

It may also be just plain poor heatset design with poor internal filtering or shielding - I would be very interested to pull it apart and see what's causing the issue since it shouldn't happen!

[poshgeordie]

Have you considered that you could have lemon headphones?

Nah - they look more banana shaped to me

There again at least they're not Apple headphones, or the ones Orange provides for their mobile phone customers