ground loop isolators for the pc?

[dafuzzbudd]

i was looking into getting a 5.1 headphone set for my pc and a reviewer said that he needed to get a ground loop isolators becasue the mouse scrolling, ect. was increased with the amp. i looked around and i only can find them for rca jacks. and at around $35 each i would need to convert it from 1/8 inch to rca then back to 1/8 inch 3 tiems for each port which is not going to happen.

anybody know of some solution i might be able to do myself for my pc? the weird thing is the back ports have no disturbance, only the fronts. i disconencted my sound system and that made no difference, the only other thing audio wise i have is a mic plugged in the back

thanks for anyone's help.

 

[FlyingPenguin]

First of all let me explain that I was a sound engineer for 20 years so I'm an expert on ground loops.

The noises a sound card produces when you scroll or move the mouse has NOTHING to do with ground loops. That noise is a cheap sound card that's allowing noises from the computer's data bus to leak through it. SOLUTION: Install a better sound card. Be aware that ALL sound cards allow SOME noise to leak through. The inside of a computer is a noisy (electrically) place. In theory a USB sound device (Creative used to sell a USB Audigy and I think they still do) is the most noise-free solution because the sound card is outside the noisy electrical environment of a computer. In practice, though, any decent quality sound card should isolate the bus noise. Some on-board sound chips tend to be noisy - my nForce2 mobo for instance passes a lot of bus noise through the sound card which is unnoticeable on speakers but annoying on headphones and I've debated installing a better sound card.

A actual ground loop is a hum, produced because two different audio devices connected to each other have different ground voltage potentials. For example, it's not uncommon to get a ground loop hum when you connect the audio output of a VCR to the audio line input on a computer - ESPECIALLY if the VCR and computer are plugged into two different electrical outlets.

Ground loops are a curse for sound engineers. Any two audio devices connected to two different power sources will likely cause a ground loop.

No one makes a 1/8" stereo isolation transformer anymore. Radio Shack used to 10 years ago - they were used to connect portable CD players to car audio amplifiers with 1/8" input jacks. I used to have one.

Hope this helps...

 

[dafuzzbudd]

why do i get this sound on the front ports and not the back?
i have onboard ac97 so what price range should i be looking at for a soundcard?

thanks a really lot for your good explanation

 

[FlyingPenguin]

Just the way the card is designed I guess. My Asus A78NX-E mobo started doing the same thing recently. Not annoying yet, but getting there. I'll probably buy a CMedia sound card.

No need to go crazy on a sound card unless you're an audiofile. Newegg sells CMedia 8738 5.1 card for $29 shipped:

http://www.newegg.com/Product/Product.asp?Item=N82E16829117107

This is as good as your onboard AC97 (I actually like CMedia better than AC97). Most mobos today use either AC97 or CMedia for the onboard sound.

 

[RichardH]

Hmm, sorry I was searching for this on google and it's high in the ranking in a search for "ground isolator" right now, so I thought I'd add my two cents.. A ground isolator might be a good first step (it's $20 and refundable if it doesn't work ). With computers, you have a sort of unique problem; while you won't get the characteristic 60 Hz hum associated with line potential differences across devices with linear power supplies, instead the computer (and perhaps your home amplifier) has a load sensitive power suppy that dynamically adjusts for load using high frequency switching to regulate the voltage and current . Therefore, the fact that the noise appears when using the breakout box on the front of the case may mean that somehow the DC offset from the switching noise in the power supply is leaking into the circuit and then being amplified on the amplifier connected to the headphones (or built into the headphones).

The sounds you're hearing when you move the mouse, load files off the hard drive, or close windows, are the changes in load on the power supply. I've experienced the same thing with my laptop, and the radio shack ground isolator fixed it up. while you lose some of the near DC sub bass ( >40Hz ) and perhaps saturate the sound a bit, it does remove the dc offset that may be interfering with the breakout part of your sound card. You'll still be sacrificing something in terms of sound quality, but I've found it's worth it. If you're extremely sensitive to the changes, it might be time to try another sound card that contains its own isolation system/ground lifting.

Of course it might be RF radiation, but most shielded audio cables, even if it is just a pigtail to a breakout box have fairly good noise rejection. On the other front, modern sound cards - even built-in ones - do have very good ground planes and are much more carefully designed than people give them credit for. The acid test is a regular pair of headphones. If you can't hear this noise on a set of passive, inductive (wire connects directly to the voice coil) headphones, the problem exists somewhere after the output stage of your sound card. If you do hear noise with headphones, then you have some kind of interference issue in your computer. and short of relocating wires or the position of the sound card itself, this may be difficult to resolve without replacing the unit.


I hope that helps

-Richard

 

[GregANDTCH]

shielded audio cables

Maybe you could put some shielding on the cables going to the front
of the case.
They probably aren't shielded.