Hall Research GLI-35mm 
Stereo Audio Ground-Loop Isolator & Filter with 3.5mm connectors
  
Eliminates ground loop noise between the audio source and TV, or audio amp
Works with all notebook and desktop PC's and all portable devices with 3.5mm mini-stereo plug
Close to perfect response of .03 db from 20 to 20,000 Hz
Perfect for AV presentations in classrooms or conference rooms
Compact and economical
 

Description
GLI-3.5mm Stereo Audio Ground-Loop Isolator & Filter with 3.5mm connectors. Eliminates ground loop noise between any audio source such as a notebook PC and audio equipment. Perfect frequency response of +.03 db from 20 to 20,000Hz. Uses proprietary audio transformers and filters for total elimination of any spurious buzz and hum in the audio.

 

Have you ever connected a PC or notebook to an audio amp or a TV and gotten all kinds of ugly noise? Most people would answer yes, and that's because the audio output from these devices are not balanced. Professional equipment have balanced audio which uses a + and a - signal for each L/R side and therefore does not rely on ground. Any noise in the ground between the source of the Audio signal and the amplifier is automatically ignored. On the other hand unbalanced signals, such as the one coming out of your notebook, have no reference other than building/AC ground. In fact you may have noticed that if you disconnect your notebook power supply and ran on batteries the noise has gone away. This is because, by doing so you inadvertently eliminated the ground loop. Line-level audio is a very tiny low-level signal, so any noise in AC ground, even as little as 0.004v, will be quite audible - yuck!

 

The GLI-3.5mm is simply inserted in series with the audio and it literally eliminates the ground connection between the two sides, passes all the audio while filtering out any noise using high performance audio transformers.

 

Everyone with a notebook should have one of these in their bag (along with an EDID emulator), so the next time you do a presentation, you will have the purest sound along with sharp and trouble free video image.

Specifications
Dimensions:1.65 " x 1.25" x 1"Matrial:ABS PlasticCompliance:CE, FCC, RoHSFreq Response:20 to 20,000Hz