audio interference from earth ground - Page 1
Forum section: electronics / general

author: Tidwell420
author_rank: Contributor
timestamp: March 22, 2013, 09:04:33 am
content: this problem has annoyed me for quiet some time i set up a computer and connect it to my hdtv for a monitor and connect the audio into an analog stereo and end up with a hum of sorts being played on the stereo nothing removes the hum until all connections to earth ground are removed from the audio source which is the computer and anything attached to it that also has earth groundso my question is. should i leave my ground connection on my computer bypassed or is there something i could do? cheaply...

author: Psi
author_rank: Super Contributor
timestamp: March 22, 2013, 09:08:34 am
content: The quickest option is to buy a $20 stereo audio isolation transformer.It will isolate the audio and get rid of the ground loop.Another option is to use a coax SPDIF or optical audio connection (If your stereo and computer have it)

author: Gall
author_rank: Frequent Contributor
timestamp: March 22, 2013, 10:39:59 am
content: A DIY solution that is simple enough: break a ground loop using a simple opamp buffer. Use the differential amplifier circuit with gain=1, connect its ground to the TV ground, treat computer's ground as the second wire of the differential output and make only a weak connection between both grounds (47-100 Ohm or so). This will break the ground loop.Before doing this, measure AC voltage between computer's ground and TV's ground. It should not exceed the maximum common mode input signal of your circuit.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 22, 2013, 04:53:24 pm
content: Upgrading to an optical connection would be your best bet. Something else you can try is to max out the volume on your PC and turn it down on the stereo. (That won't eliminate the noise but it will attenuate it.)

author: Tidwell420
author_rank: Contributor
timestamp: March 22, 2013, 07:38:53 pm
content: i did start with an optical digital connection but before one year could pass my surround sound stereo system decided to call it quits that sound system simply does a power on loop after attempting to power on display says welcome for about 5 seconds then goes blank then back to welcomei spent a month trying to figure out why but seeing how my only test equipment i own is simply a multimeter i couldn't track the problem

author: David_AVD
author_rank: Super Contributor
timestamp: March 22, 2013, 09:50:09 pm
content: The audio transformer option is guaranteed to work. The only issue may be some loss of bottom end (deep bass) depending on the quality of the transformers.

author: Tidwell420
author_rank: Contributor
timestamp: April 22, 2013, 07:44:03 am
content: Quote from: David_AVD on March 22, 2013, 09:50:09 pmthe way my bass setup works i could very easily compensate for loss of the bottom end in fact my subs have there own gain control which is currently turned way down as to not annoy the neighbors

author: ptricks
author_rank: Frequent Contributor
timestamp: April 22, 2013, 12:19:52 pm
content: Have cable internet service ? Most likely it is from that cable , either on the cable modem, or tv connections. You can get a cable isolator and that will benefit everything connected.http://www.amazon.com/Viewsonics-VSIS-EU-Cable-Ground-Isolator/dp/B0017I3K9M

author: madires
author_rank: Super Contributor
timestamp: April 22, 2013, 12:39:33 pm
content: Quote from: ptricks on April 22, 2013, 12:19:52 pmAre you forced to connect the braid of the cable to the equipotential bus bar just where the cable enters the building? I'm just curious :-)

author: ptricks
author_rank: Frequent Contributor
timestamp: April 22, 2013, 12:47:24 pm
content: Quote from: madires on April 22, 2013, 12:39:33 pmMost electrical codes state the cable connection has to be attached to a grounding block that has its ground wire attached to the same ground as the homes electrical service.Sometimes you don't need a transformer for isolation , you can use 1000pf caps in series with the ground and rf center wires if it is a DC issue. Sometimes the cable companies amps leak a little DC into the RF .