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Shamrock

Fans causing speaker noise

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Hi folks. This is making me kinda crazy so I hope someone has some advice, please and thanks.I just moved everything to a new case and found that the (included) case fans seem to be causing interferance with my speakers (1 sub, 2 sats) when plugged into either the rear or front audio port. The same problem presents on headphones when in the front, but not the back. I had 2 other fans hooked up at the front. The noise was less severe when they were removed, but still present and quite loud.It's the first time I've had front audio output, but I can't imagine this is normal, nor can I imagine that a default installation would be prone to this. Anyway, I wonder if anyone here has any suggestions as to the cause and or solution.Supplemental info:The case is an Aspire X-CruiserMB is an AOpen AK77-600N - Socket AUsing on board AC97 sound - could this be the problem?Please let me know if you need more info.TIA

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My first thought would be a weak and/or noisy 12V rail on your power supply. I'm not sure if the 12V rail is used for the audio stages, but that would make sense. On the other hand, RF noise could be propagating over to the other rails as well.If you could narrow it down to one fan, it could be an electrically noisy fan, but it doesn't sound like that from what you're describing.What's the rated amperage on the 12V rail?Kevin

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try brushless fans (ones with ball bearings are better too, not from an electrical noise, but from a mechanical point of view...)a brushless fan does not use brushes (duh...) to cause the fan to work.brushes cause electrical noise by contacting, then not contacting the armature (i.e., make sparks)

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My first thought would be a weak and/or noisy 12V rail on your power supply. I'm not sure if the 12V rail is used for the audio stages, but that would make sense. On the other hand, RF noise could be propagating over to the other rails as well.If you could narrow it down to one fan, it could be an electrically noisy fan, but it doesn't sound like that from what you're describing.What's the rated amperage on the 12V rail?Kevin
Thank you both for your replies. I have no idea of the correct amperage. I'm pretty useless when it comes to matters of electronics like this. Temmu, I appreciate your input, but I am looking for a solution that doesn't involve any new purchases if possible.If that info is available from the power supply, just tell me what to look for and I'll post it. Anyway, the fans are connected via Molex to the psu and the fan speed controller, so I guess it's all at 12V? Needless to say, at high speed the fans cause a bigger (electrical) noise than at slower speed. The thing I don't get is that I can't see selling something that is going to perform like this out of the box. I can't help but think the problem must be peculiar to my setup. I really hope it isn't the power supply that's at fault.

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The PSU is 420W, the sticker shows 17, 25 adn 14A on the 3.3, 5, and 12V rails repectively.Supplemental: When I used the dial volume control on the line frunning from the speakers, it reduced the amount of noise to an almost acceptable level but it persists. Fortunately, the POS is willing to accept exchange of the psu. I wasn't certain about that since it came with the box. (I thought they'd only take all or nothing.) I wish I could be more certain that is the cause but since I planned to upgrade the PSU it came with anyway, I might as well give it a go.

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I know it's been a while since the last post here. Sorry about that. I wish to report that I have replaced the power supply with a better aftermarket model and the noise persists, unfortunately.I've managed to get the amount of noise down to an almost acceptable level by adjusting downward the volume control on the speakers themselves but it's still there. I could really use some advice.

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Try this.Get a few "RF" Choke's and thread the fan's leads thru the center of the choke. You may find this helpful. I'd tell you where to get tham but since your in Canada I am not fimilar with stores available to you.Also when you installed the board on the case did you put the felt pads between the board and the brass stand off's?

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Try this.Get a few "RF" Choke's and thread the fan's leads thru the center of the choke. You may find this helpful. I'd tell you where to get tham but since your in Canada I am not fimilar with stores available to you.
I'm not too sure what these are, but I imagine that if I find the right store they will be able to help so I'll look into it. Thanks.

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Anyway, the fans are connected via Molex to the psu and the fan speed controller,
Why don't you bypass the controller and plug the fans direct, and see if the problem goes away.

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Sorry for taking so long to respond. Ok, so sometimes, I'm quite the bozo. After bypassing the fan speed controller, I found that the noise was all but eliminated. I really should have tried this sooner. However, upon closer inspection, I found the speakers were still generating the same noise, but at a much lower level. I.e. if you put the speaker to your ear you can still hear it but barely otherwise. In a previous post, I mentioned that lowering the volume on the speakers themselves produced a reduction in the effect. Now, increasing the volume resulted in a small increase but nothing like it was before. So, any ideas as to what I might do to correct this issue? This is tolerable but my original objective was to add additional cooling and use the fan speed controller to reduce noise when extra cooling is not required. I could rma the case but that would be almost more trouble than it is worth. It may seem petty, but I am a bit obsessive about things working the way they are supposed to rather than being just good enough to do the job. It seems to me, this should not be a normal occurrence for purchasers of this particular product. So, I am wondering what I might have done to cause it or if it is something about my other hardware.I'd appreciate any assistance. TIA

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We face the exact same problem at the location my church uses to meet. There are rheostat controlled lights that, when used, put a buzz in our speakers. The solution for us was to get power conditioners for all of our equipment.Not sure what you can do.... it may require you to purchase a better fan speed controller.

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Thanks for the reply. Unfortunately, the problem persists even without the controller in the mix. I am starting to become really curious as to the cause of this noise.

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If you have to turn the speakers up really high to hear the noise now, then that is normal. If you unplug the speakers from the sound card, you should still hear some his, if only a little bit, and that is very normal. The amplifiers in speakers are typically noisy, creating that hiss. Even my high end THX certified speakers generate noise.I would check to see if unplugging the speakers results in less noise. If it is noticable, you may want to inves in a Sound Blaster Live or Audigy card, since those cards are VERY quiet.Hope this helps. ;)Adam

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Thanks for the reply."I would check to see if unplugging the speakers results in less noise. If it is noticable, you may want to inves in a Sound Blaster Live or Audigy card, since those cards are VERY quiet."Alas, when unplugged from the computer, they are totally silent. I would draw your attention to something I thought I mentioned before but may not have. When I plug headphones into the rear connector there is no noise. When plugged into the front panel connector, the noise intrudes at any volume, and perists on the speakers no matter where they are plugged in. HTH.[EDIT] That was before, when the fan controller was connected. Now, I've switched them around, i.e. plugged the speakers in the back and the headphones in front. Nary a peep. Does this help? The fan controller is still being bypassed. If I get the chance to hook it up and report back, I will. But does this give you any ideas as to the cause?Thanks for your help folks.

Edited by Shamrock

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the back plug is very close to the amp source and has little opportunity to receive interference.the front plug would have several inches of possibly unshielded (or shield not properly grounded) wire. the wire is an antennea and gladly relays the noise produced inside the pc.i agree with ross549 in that the amp in most pc speakers will be on the noisy side.

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Keep in mind that the sound card may also be producing some level of noise, which the amp in the speakers will pick up and amplifiy with its own noise.

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Ok, fair enough. Let us assume, for a moment, that the issue lay somewhere in the sound system or front panel wiring, and that I will attempt to address it with the chokes described previously. Where would you suggest their placement?

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nearest the front jack.psthis leaves the antenna on the far side of the jack with a very short piece of wire, er antenna, near the jack.

Edited by Temmu

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