Weird Problem with Tripath amp and HTPC - diyAudio
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Old 26th January 2009, 12:00 AM   #1
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Default Weird Problem with Tripath amp and HTPC

Hello - I have one of the sure-electronics cheapo tripath boards from ebay driving my frugal horns. I built a new HTPC and when I use the on-board audio I get a weird low frequency humming that only happens when you move the mouse, scroll through a page but is almost constant with any programs running.

It is the strangest thing because the amp works fine with all 3 other computers (1 desktop, 2 laptops), mp3 players, etc.

On the other hand, when I hook up my seinheiser canal phones to the HTPC I can't hear the noise / interference at all.

I am at my wits end troubleshooting the HTPC. I have carefully isolated the motherboard from the case, removed all components except processor / memory / hard disk, Flashed BIOS, upgraded all drivers, muted all inputs and outputs other than the ones being used, swapped out the cable between PC and amp and the problem persists.

It is almost like these two particular components just don't like each other. Both seem to work fine on their own and I would rather not RMA the board if I can sort this out.

Suggestions?

Thanks in advance
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Old 26th January 2009, 08:06 AM   #2
CJ900RR is offline CJ900RR  Sweden
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I have been having this problem to in a computer, and the solution where to update the drivers to latest one. But I cant recall witch driver, it was either the chipset drivers (Nvidia in my case) or the drivers for the graphic card (also Nvidia).

I dont know if this will help you but give it a try anyway. I did not expect that behaviour because of those faulty old drivers, but it did solve the problem.
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Old 27th January 2009, 10:06 PM   #3
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Could be rf interference on the audio, try an rc rf attenuator to filter it out.
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Old 30th January 2009, 01:25 PM   #4
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I'm assuming on-board audio is the motherboard audio chip. Have you considered a dedicated sound card?
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Old 30th January 2009, 06:14 PM   #5
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You have a hardware problem with your board. When you move a mouse or scroll through a pages etc there is current demands appears in a circuitry of your board and it can't handle it properly because some component or components are shorting a bit or there could be any other reason why board isn't working. Check electrolytic caps on your board / replace PSU / replace your board.

Regards.
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Old 31st January 2009, 12:39 PM   #6
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Quote:
Originally posted by CJ900RR
I have been having this problem to in a computer, and the solution where to update the drivers to latest one. But I cant recall which driver, it was either the chipset drivers (Nvidia in my case) or the drivers for the graphic card (also Nvidia).

I dont know if this will help you but give it a try anyway. I did not expect that behaviour because of those faulty old drivers, but it did solve the problem.
Ah, updated chipset drivers do help, as does Geforce 175.19 (when applicable).

Also, possible that some of the many extraneous sound inputs aren't muted because they don't show up. The Properties selection on the windows volume control software can usually gain access to all of these.

And, Drew Kaplin at Dak, did import some audio isolation transformers to stop sound card to amp buzz. However, if that amp is a tripath, perhaps it cheaper to run it from the same power supply as the source so that there's only one ground, doing it the easy way? And, if your power supply isn't up to it, then you've found your problem already.

Some boards, namely BioStar and ECS, have a jumper marked USB Power, which determines the S3 wakeup state for USB and PS/2 connections. That can make a difference in the way that these ports are powered.

If your CPU is AMD64, then turning off the defunct "cool-n-quiet" cpu feature may help stop noise. Its almost always listed as an option in the Bios. That feature is problematic at best, and even worse with Vista. Most soft coolers rocket the mainboard speeds, and/or component interconnect state, up and down on demand. The old Intel 945 doesn't make noise when soft cooling (because it doesn't ever quite halt successfully), but most other computers dislike having their parts turned on and off many times per second because it does make noise.
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Old 1st February 2009, 12:43 AM   #7
jaycee is offline jaycee  United Kingdom
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Location: Norwich, UK
Onboard audio is often susceptible to digital breakthrough. First off, don't use a cheap power supply in the computer - get a decent one. If it's cheap, it's crap.

Second, check that your system's chassis is connected to safety ground (or Earth as we call it here).

Finally, see if the Tripaths have an ultrasonic filter on the input. This is typically a low pass filter made from a resistor in series with the signal, and a small capacitor (say 220-470pF) to ground after it. If it doesn't have that, try adding one. Usually the resistor will be present, and it is just a matter of identifying it and adding the small capacitor.
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