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 Audio bleed-through of electrical noise 
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Joined: Fri Apr 24, 2009 7:00 pm
Posts: 12
Post Audio bleed-through of electrical noise
I just received my Fit-PC2 this week and got it running today with my HDTV setup. Everything I've tried seems to be working fine except that when outputting the HDMI video and 2.0 audio to my HDTV and AV Receiver I'm getting a low audio hum/buzz noise through the receiver's speakers.

It seems to vary depending on how loaded the CPU is at the moment - when Firefox is running (this is the WinXP version of FitPC) the bleedthrough noise is louder and higher-pitched than when just sitting at a blank desktop.

It's not loud, but loud enough to be heard when music or other sounds aren't being played and definitely loud enough to be annoying.

Any suggestions? I'm thinking a more heavily-shielded audio cable might work, but don't want to go buy one unless that's a demonstrated fix. Also considering a USB-to-optical audio adapter, but the PC should provide 2.0 output without background hum.

Thanks.


Sat Jul 11, 2009 7:05 am
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Joined: Mon Apr 27, 2009 12:29 pm
Posts: 58
Post Re: Audio bleed-through of electrical noise
My experience with on-board sound cards has always been pretty bad (I could tell which program was running on my laptop by listening to the sound through external speakers), so I'd suggest you simply get an USB sound card.


Sat Jul 11, 2009 4:54 pm
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Joined: Fri Apr 24, 2009 7:00 pm
Posts: 12
Post Re: Audio bleed-through of electrical noise
I've already got one on order - a USB-Toslink optical adapter. I'm serving music from the Fit-PC2 to Squeezebox devices, so this will just be a fancy way to hear the computer's ding noises.

But I do hate hum and buzz, so hopefully this will take care of it.


Sat Jul 11, 2009 5:11 pm
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Joined: Sat Jun 20, 2009 7:42 am
Posts: 5
Post Re: Audio bleed-through of electrical noise
I have two suggestions:

1. Make sure the audio plug is seated all the way into the output jack. I had to push fairly hard the first time I connected speakers before it went all the way in. The plastic casing of the stereo mini-plug should be touching the top of the jack with no metal from the plug should be showing.

2. Mute the line-in and microphone inputs, if there is nothing connected to them. I was picking up a lot of noise from the line-in, especially.

That said, I still get a good deal of distortion in the left channel. The right channel seems ok.


Sun Jul 12, 2009 4:37 am
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Joined: Fri Apr 24, 2009 7:00 pm
Posts: 12
Post Re: Audio bleed-through of electrical noise
Both good suggestions, but unfortunately made no difference.

My audio plug was seated all the way previously, and muting EVERYTHING (including the master volume) made no difference - it's a pretty fundamental bleedthrough.

So I suppose I just have to sit tight and wait for the USB-to-optical audio adapter to show up - I figure that should fix the problem even if it's overkill.

Thanks for the ideas.


Sun Jul 12, 2009 8:15 am
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Joined: Fri Apr 24, 2009 7:00 pm
Posts: 12
Post Re: Audio bleed-through of electrical noise
Attempting to work around the hum issue, I purchased this USB-to-optical5.1 adapter:

http://www.cablestogo.com/product.asp?c ... &sku=22327

The unit "works", but the audio is grossly distorted - it sounds as if it's being horribly overdriven at very high levels by the Fit-PC2; even if I turn down all the various volume/mixer settings, the audio is still very distorted, just at a lower volume level. I've tried both the analog 2.0 and optical 5.1 outputs, and different AVR inputs, with the exact same results. Also tried outputting to my other PC's Logitech speakers instead of the AVR system - same problem.

The WinXPHome that shipped with the Fit-PC2 identified and installed this USB device and doesn't report any driver issues (I have not installed any additional drivers for this product).

Cables To Go sent me another unit to try, and it works exactly the same way, so it's not a hardware-failure issue with this product.

Can anybody from Fit-PCs USA reseller network please give this product a try and see if they can duplicate/resolve the issue? If I can get it working properly, it'll really make my HTPC system complete.

Thanks very much.


Fri Aug 07, 2009 9:54 pm
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Joined: Mon Mar 16, 2009 2:11 pm
Posts: 2339
Post Re: Audio bleed-through of electrical noise
fit-PC2 audio codec is not involved in this setup.
- The distortion might be typical of that adapter - you may check that by connecting it to another PC.
- Try to obtain specific device drivers for this adapter.
- fit-PC2 audio drivers might interfere. Try disabling them in device manager.
- In theory there could be some inconsistency in USB bandwidth, but this is unlikely because the device is low bandwidth USB 1.1 and this problem is not expressed as distortion.

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Irad Stavi
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Fri Aug 07, 2009 11:08 pm
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Joined: Thu Aug 06, 2009 8:04 am
Posts: 3
Post Re: Audio bleed-through of electrical noise
The Fitpc is not at fault. Your reciever is making the "electical noise" or as its more refered to as AC hum. Shielding would help, but I do not believe that it is the issue at hand. It sounds like a grounding issue. AC hum can be solved by many different methods. At radioshack they sell magnets that you place an your audio cable to reduce noise. I cannot remember there name, but they are about 3 bucks. Another option is to tie your grounds togather on your setup. If you amp only has a two prong connection to the wall, there is a screw terminal that is exposed and must be connected to earth ground. Connect it and make sure your TV is connected to that same ground. I would highly recommend using you HDMI audio or another DIGITAL device. Digital audio is not capable of making noise, how ever your switching power supply can. Grounding is everything in the audio world.


Sat Aug 08, 2009 12:56 am
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Joined: Fri Apr 24, 2009 7:00 pm
Posts: 12
Post Re: USB 5.1 Audio adapter not working properly
irads wrote:
fit-PC2 audio codec is not involved in this setup.
- The distortion might be typical of that adapter - you may check that by connecting it to another PC.
- Try to obtain specific device drivers for this adapter.
- fit-PC2 audio drivers might interfere. Try disabling them in device manager.
- In theory there could be some inconsistency in USB bandwidth, but this is unlikely because the device is low bandwidth USB 1.1 and this problem is not expressed as distortion.

Thanks for the reply.

I have tried the adapter on my notebook and desktop PCs (both Dells running WinXPPro) and it works perfectly. The USB connection auto-detects and even switches back to regular system audio when I unplug the USB audio adapter. No driver installation necessary.

On both of these machines, the sound was high quality and undistorted.

Have tried disabling the FitPC audio drivers in Device Manager; no difference. I have searched and contacted Cables To Go; there are no supplemental drivers for this device - Windows autodetects it and from there I just go to audio settings to tell it to use USB Audio and the 2.0 or 5.1 speaker configuration depending on whether I'm connecting to analog or optical output. As mentioned above, on my other WinXP systems it does work well without supplemental drivers.

For now I'm concluding there is a problem in the FitPC, either my unit, the design or the BIOS/driver package. It'd sure be great if your tech guys could take a look at this audio adapter; for the money it's a great and inexpensive solution to get 5.1 digital audio if it can be made to work - and I've demonstrated it CAN work on other systems.


Mon Aug 10, 2009 6:42 pm
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Joined: Fri Apr 24, 2009 7:00 pm
Posts: 12
Post Re: Audio bleed-through of electrical noise
DJ-KhaosTheory wrote:
The Fitpc is not at fault. Your reciever is making the "electical noise" or as its more refered to as AC hum. Shielding would help, but I do not believe that it is the issue at hand. It sounds like a grounding issue.

Thanks for the idea, but have already tested that. Used the same cable/input to the AVR as the FitPC was using, connected to MP3 player and boombox - no hum.

This hum won't matter at all if I can get the USB 5.1 audio adapter (above) working properly to bypass the internal analog audio circuits.


Mon Aug 10, 2009 7:05 pm
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