Computer audio out very noisy?

[downhiller80]

First of all I'm a long-standing member but couldn't get my old account using, not posted for a couple of years.

My speakers recently died, which led me to use headphones for a while. I couldn't believe the amount of hiss on them, I'd assumed my aging speakers were the cause of the problem before, but it seems it's my line-out that's the issue.

I've just acquired a new 5.1 system and have the same problem. Tried plugging them into the TV and my mac mini instead and they're totally hiss free, so it's definitely the PC. I'm not talking about a minor amount of hiss either, it's very noticable, and quite apparent even with the speakers turned down to 0.

Have tried bundling the RCA cable up right behind the PC when connected between telly & speakers, no noticable hiss from that so it's not just a badly shielded PC interfering with badly shielded cables. I've also tried different cables, no difference.

Is it common for PC sound devices to deteriorate in this way over time, or might it indicate that my motherboard's backpanel is shorting against the case in a way it's not supposed to, or something like that?

The board's a Gigabyte GA-P35-DS4, just in case any of you happen to know it's a common fault with certain chipsets or something. However, I've also plugged in a separate PCI sound card and had the exact same issue, and even tried a USB sound-thing which I was SURE would cure it... but didn't!

So, PSU/motherboard issue you think? Zalman 500W heatpipe PSU. Known fault?

Reckon it'll be doing damage to more sensitive things like my hard drives?

Thanks guys!

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[downhiller80]

I wondered if it might be my surge protector, but have just ruled that out. Also plugged into a completely different room in case I had a dodgy wall socket.

Disconnected all external things (USB, network, monitors) and still get the same problem.

Opened up my case and had a wiggle of all of the PSU connectors. Tightened the motherboard grounding screws. No help.

 

[downhiller80]

Took out my 2 data hard drives. No help. Disconnected DVD drive. No help.

Also seems worth pointing out that I can "hear" my PC through the static. Hard disk seeks induce a different noise. A white screen versus a screen of text induces a different noise, etc etc.

So, is my PSU bummed?

 

[kamikazekyle]

If you're hearing buzzing, "moaning", or some other odd sounds that aren't plain 'ol hissing, then it's probably a grounding issue with the system. Since it seems to happen even with addon cards, I would point a suspicious finger at the power supply.

I have an HP tablet that had BAD buzzing and hissing when using anything but the internal speakers. I got tired of it, yanked the third grounding prong off the power cord, and have had fine sound since.

Of course, removing the grounding plug isn't exactly a recommended solution, what being a potential hazard and all that.

If you're talking about just hissing, it could be the line out overamping the signal. Some line-outs might be pre-amped. But, since you mention that the background noise changes with the computer's display/HD activity, I would lean towards a grounding issue.

 

[downhiller80]

I agree, sounds like grounding issue to me. I don't understand how removing the earth pin from the plug helps though? I feel I should since I did a physics degree, but it was many years ago and electronics was always my weakness.... care to explain?

Just installing a USB ubuntu image so I can rule out some weird software thing, though I'm 99% certain it can't be a software issue.