Computer noises through speakers

[Vincent Oliver]

I have a Firestudio Mobile external sound card which uses the Firewire port, whenever I move the mouse or open a new screen I get a rustling noise from my speakers. It is very annoying, last week I purchased the Focusrite 214 (USB) in the hope that the problem would be cured, alas no such luck, I still get the same rustling noise when windows open or mouse movement. Does anyone have a cure for this.?

Many thanks in anticipation or a solution.

[Gary Nattrass]

A lot of computers do this and it is mostly the cheap and nasty sound card built into them which also has an unbalanced output.

I managed to cure this by using my blackmagic HD card to output the audio in balanced line level to my digidesign desk which then feeds my monitor amp.

[Jay Massengill]

Please describe precisely the audio chain from your computer to your speakers and how they are powered.

[Vincent Oliver]

Thank you Gary and Jay for your feedback and interest.

Jay,

I have the Presonus Firestudio mobile which uses the Firewire port and the Focusrite Scarlet 2i4 which uses the USB port. I am using the TRS (balanced) connection for my Yamaha monitor speakers. Nothing more complicated than that. The CPU noise happens when I move the mouse or open a window or open a web page with lots of images. If I use the power adapter with the Firestudio then the noise is virtually eliminated, the Focusrite uses power from the USB port.

[Jay Massengill]

When you monitor your interfaces from their headphone jacks using good headphones do you also hear the noises from the computer?

Also, where do you have your interfaces located physically in relation to the computer and its monitor?

[Vincent Oliver]

Hi Jay,

No, both the FireStudio and Focusrite are totally silent with Headphones attached ( Sennheiser HD 25)

The computer is under the desk and the interfaces are approx 4 foot away.

[Jay Massengill]

Next I would connect the audio line outputs from the interface to some other audio device like a recorder or a mixer that you can also monitor with headphones. If that's clean then it has to be your speakers or their AC power connection in relation to the computer AC power, or the precise location of the audio cables going into the speakers in physical proximity to your computer or computer monitor.

If that test has noise, then it could be your cables are bad or aren't wired correctly for a balanced connection.

Which Yamaha speakers do you have? And what type of computer monitor?

[Vincent Oliver]

Jay, I have just had a "Doh" moment and looked at the cables I see that I am using unbalanced jacks, i.e. only two contacts per plug. Do you think using a Balanced TRS cable will cure the problem? or should I be using that anyway? I did think I was using TRS cables as previously stated in an earlier post, I guess we shouldn't always assume without checking first.

[Jay Massengill]

Balanced cables are certainly worth a try, it might solve the problem easily.

[Vincent Oliver]

I have ordered a pair of Balanced cables, will let you know if they cure the problem.

[Steve House]

Just FYI, the computer noise could actually be radiated from the monitor or the monitor cable as well as the CPU. Also, not all speakers are well shielded and they could be picking up the RF directly.

[Vincent Oliver]

I will experiment with the placement of the speakers or monitor and see what happens, I am putting all my hopes into the Balanced cable option, fingers crossed.

[Vincent Oliver]

The balanced cables option didn't work, just tried them. I also tried putting in a dedicated USB & Firewire card, again not a solution. I am stumped.

[Jay Massengill]

What type of computer video monitor do you have?

Do you have any other device you can connect your interface to with your new balanced cables, and monitor that device with headphones to make sure the problem starts happening when the signal reaches your speakers and not before?

I don't know if this would work, it really shouldn't be needed, but plugging your speakers AC power into a line filter like this one:
http://www.bhphotovideo.com/c/product/651629-REG/Gefen_GTV_PLC_FEU_GTV_PLC_FEU_Power_Line_Filter.html

Can you connect your audio interfaces to your speakers (sitting in the exact same spot) but running from a different computer like a laptop? Then confirm that signal path is clean independently. Next move the mouse and open up some windows on your main computer and listen if that still induces the sound on your independently connected speakers.

[Jens Korsgaard]

I reckon the balanced cables might fix this, however, just out of curiosity, can you give us a little more information as to the computer specs? For instance, do you have a wireless lan card or the like installed? Its rare, but some of the added PCI components can cause the effect you are describing. I've had it happen more than once on different setups.

Also, just to be sure, have you completely turned off the onboard soundcard device? I realize that the firewire likely overrule whichever soundcard you have, but from time to time the onboard card will act up, if not turned off entirely.

Again, I doubt its any of those, but those are easily checked while you wait for the cables to arrive!