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Topic: Static/Load noise from onboard sound to active monitors (Read 3863 times) previous topic - next topic
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Static/Load noise from onboard sound to active monitors

The PC I use has a VIA VT2021-based audio system. The active speakers produce a considerable amount of noise, but some monitor headphones on the same analog port on the PC output only a minimum amount of load noise. The monitor itself without any cables attached has a very low-volume humming, on its analog-only line of its embedded mixer. This is amplified the moment I connect a cable to one of the speaker's analog inputs, before the other end even connects with the PC, and becomes loud if the tip of the connector contacts things like my skin or a big metallic object. Is there something I could do to moderate the noise, without spending much on new hardware?

Static/Load noise from onboard sound to active monitors

Reply #1
I just realised I posted it on the wrong forum. Mods, please move to hardware

Static/Load noise from onboard sound to active monitors

Reply #2
This sounds like a grounding problem. As long as the speaker circuit is not grounded, line voltage will be capacitively coupled into it.

Normally whatever you connect the speaker's input to will be grounded, and will then ground the speaker's circuit through the cable's shield.

Do you still hear hum when the speaker is connected to the PC's analog line out (I assume the PC's chassis is grounded)?

Edit: typo

Static/Load noise from onboard sound to active monitors

Reply #3
The humming persists even when I conclude the connection to the PC analog out, albeit a little attenuated comparatively to the speaker side only cabling. As for a grounded chassis...I don't know what to look for here so I can tell.

Static/Load noise from onboard sound to active monitors

Reply #4
Does the power plug to the PC have three prongs, one of which goes to powerline ground?

Static/Load noise from onboard sound to active monitors

Reply #5
Quote
This is amplified the moment I connect a cable to one of the speaker's analog inputs, before the other end even connects with the PC
That sounds like an unshielded cable, or a cable with a broken ground/shield connection.

Do you have another cable to try?

Quote
The humming persists even when I conclude the connection to the PC analog out, albeit a little attenuated comparatively to the speaker side only cabling.
If it gets better when you plug it in, it's probably an unsheilded cable.  If it gets worse the ground/shield in the cable is probaby broken.

Quote
...on its analog-only line of its embedded mixer.
What kind of connection is that?  Is it stereo or mono?  If it's a balanced (3-wire) XLR or TRS connection, you could have the wrong adapter/cable.

Quote
...and becomes loud if the tip of the connector contacts things like my skin or a big metallic object.
That's normal.  Your body picks-up electomagnetic energy from the AC power all around you.  A higher impedance input will be more sensitive to this, but it happens with any line-level input.  Sometimes you can do a quick test of an input by touching the connection, but you have to be careful with high-power amps (because you could blow a speaker).

Static/Load noise from onboard sound to active monitors

Reply #6
Does the power plug to the PC have three prongs, one of which goes to powerline ground?


Yes.


Do you have another cable to try?


What kind of connection is that?  Is it stereo or mono?  If it's a balanced (3-wire) XLR or TRS connection, you could have the wrong adapter/cable.


I have tried 3 different cables thus far:
-one 3.5mm TRS (PC side)? L/R RCA (analog-only line of the speaker, noisier one of the two)
-two 3.5mm?3.5mm TRS (digital/analog line of the speaker)

quality: ...CHEAP!

 

Static/Load noise from onboard sound to active monitors

Reply #7
Quote
I have tried 3 different cables thus far:
-one 3.5mm TRS (PC side)⇨ L/R RCA (analog-only line of the speaker, noisier one of the two)
-two 3.5mm⇨3.5mm TRS (digital/analog line of the speaker)

quality: ...CHEAP!
I guess we can rule-out a broken ground/shield on all 3 cables.  It's also very unlikely that the speaker's internal ground connections are broken to both the 3.5mm and RCA connectors.

I'd also be surprised if all 3 cables are unshielded.  But, if it hums when you plug-in a cable that's open at one end, that strongly suggests an ineffective shield.

If you want to buy some new cables online, and if you live in the U.S., try these from Monoprice.  They are heavy-duty and high-quality, but very inexpensive...  Buy a couple extra to make the shipping cost worthwhile.

Static/Load noise from onboard sound to active monitors

Reply #8
Disregard, misread the OP.

Static/Load noise from onboard sound to active monitors

Reply #9
Multiple units connected together AND with 3 wire power cords sometimes have hum and noise issues. We cannot defeat the 3rd wire ground but we _can_ isolate them with something like this.

http://www.amazon.com/s?ie=UTF8&page=1...n%20Transformer

The truly HiFi folks might grouse about transformers - balanced line is technically better and and transformerless balanced is the best in analog. In the real world, very few folks would be able to ABX it. It's cheap and easy and if you do decide you want to throw money at it, you can knowing it will solve your problem. I'm using an isolation module on cheap computer speakers and it works fine. I'm also using the more advanced system for the 2 receivers also connected to the same PC. All do the job I expect.


Static/Load noise from onboard sound to active monitors

Reply #10
Is this Ground Loop Isolator suitable? It says it's for car sound systems, so I dither a little.

Static/Load noise from onboard sound to active monitors

Reply #11
Quote
Is this Ground Loop Isolator suitable? It says it's for car sound systems, so I dither a little.
That should work (if ground isolation is going to help).  It's line-level, and it's passive (it doesn't need power from the car).