Audio interferance

Hi,

Anybody got any bright ideas on how to solve audio interferance / noise from a PC?

Got my PC going through a mixer (nothing wrong with the mixer) and the interferance noise coming from the PC is quite bad - thing is - it actually goes alway when the hard drive is being accessed! Wierd....

Any ideas?

[Kymmy]

Problem with PC's is that it's a whole lot of electrical frequencies in one box which means any electrical connection to it also carries a load of Sproggies, I used to get the same so started using a SPDIF cable (even better is optical) for the audio as digital is a lot less susceptible to harmonic interference. Doesn't though help you much with the mixer unless you have a digital in.

[Halcyon]

Is this a separate sound card or an onboard one?

If onboard it is likely to cause noise as and when you access the PC. The amplifier within the mixer will also be picking up on this and thats why it will be more apparent.

Also check you do not have your audio cables touching power cables. This can also lead to more noise.

I used to have this problem with noise and got a seperate PCI soundcard which solved it.
I use this one:

http://www.dolphinmusic.co.uk/produc...hz-24-bit.html

It's the onboard sound chip. My Yamaha SW1000XG had to be pulled and put into my other computer as there are not any 64 bit drivers for it.

Thanks for the SPDIF tip Kymmy - unfortunately it does not have any digital inputs.

I have an old SB Audigy - but I think the audio out connection is duff on it...

[Jon T]

It's likey to be the motherboard noise finding it's way on to the output of the onboard soundcard, either that or a ground loop.

[Stuart]

For sound recording, we use these at work. Bit expensive, but they've been out a couple of years so I would be surprised if you couldn't find them a lot cheaper.

USB powered. Two channel inputs (6 1/4 inch or XLR). Both with gain controls. XLR is phantom powered. SP/DIF in/out/passthrough and a separate headphone output. In short a basic mixer as well.

[Delta Whiskey]

Are there any audio cables inside the case that could be re-routed away from noisy areas, things like the cable connecting the motherboard to front panel headphones/microphone.
It might be worth putting ferrite beads on such cables. https://secure.wikimedia.org/wikiped...i/Ferrite_bead

[Jon T]

Originally Posted by Delta Whiskey

Are there any audio cables inside the case that could be re-routed away from noisy areas, things like the cable connecting the motherboard to front panel headphones/microphone.
It might be worth putting ferrite beads on such cables. https://secure.wikimedia.org/wikiped...i/Ferrite_bead

Ferrite beads rule, especially in a mixed audio/RF environment.

Originally Posted by Kymmy

Problem with PC's is that it's a whole lot of electrical frequencies in one box which means any electrical connection to it also carries a load of Sproggies, I used to get the same so started using a SPDIF cable (even better is optical) for the audio as digital is a lot less susceptible to harmonic interference. Doesn't though help you much with the mixer unless you have a digital in.

SPDIF in its modern form covers both coaxial and optical connections

http://www.topbits.com/spdif.html

I thought ( but I am not sure on this as its not my field) that as long as enough information is passed digitally even if slightly corrupted gets corrected ?

[Uncle Peter]

Always used balanced connections between your audio interface and the mixer. Also, try to use balanced connectors to your monitors. Balanced lines reduce the likelihood of interference as the cables have an additional level of shielding over a 2 conductor unbalanced link.

Common balanced connectors are: 1/4" or 1/8" TRS (tip, ring and sleeve) jacks or XLR

The problem is that your Audigy sound card possibly doesn't support balanced connections

ps: digital solves a lot of problem as above but I doubt you have a digital mixer

[Kymmy]

Originally Posted by zing

I thought ( but I am not sure on this as its not my field) that as long as enough information is passed digitally even if slightly corrupted gets corrected ?

Nope, there's no parity or error correction on SPDIF unlike newer systems (like AES) it does have a few extra bits in it's 20bit format but they're used for equipement type and copy protection codes. Remember also that SPDIF isn't synched as it's one way only so does have a sync fallback but still can't correct errors (instead it just misses out the corrupt section)

In this case though I suggested it purely due to it's supression of analogue harmonics whether you use coaxial (some motherboards do have SPDIF co-axial) or Optical is dependant on what's available and what you're plugging it into

mine has both as does my amp

[Kymmy]

I have SPDIF on the motherboard (old asus) but regulary use optical or co-axial via my cambridge audio DTS decoder with the multimedia players and SAT

Lee, check your onboard sound chip, if it's only a few years old you might find that you have an SPDIF header onboard, an old SPDIF decoder on ebay will be dirt cheap and will enable you to plug directly into your mixer/amp

Originally Posted by Delta Whiskey

Are there any audio cables inside the case that could be re-routed away from noisy areas, things like the cable connecting the motherboard to front panel headphones/microphone.
It might be worth putting ferrite beads on such cables. https://secure.wikimedia.org/wikiped...i/Ferrite_bead

Nope - all cables are external - plugs into the 3.5mm jack.

My cables go into a cable tray in my desk - worth moving the audio cables out of there?

[Uncle Peter]

Does the Audigy card have a drivebay mounted break-out box connected via ribbon cable?