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What causes low level hum from audio chipset?

Discussion in 'General Hardware' started by twilyth, Jun 19, 2011.

  1. twilyth Guest

    I have the HDMI out from my graphics card going to my HDTV. The other output goes to a monitor. The 2 are set up so the desktop spans the monitor and tv.

    But that shouldn't really be important. For the audio, I have 1/8" extension cord with a 1/8" stereo to 2 RCA jack adapter. That goes to one of the receiver's audio inputs.

    The PC is on a 3 prong outlet so as far as I can tell, everything should be grounded.

    The chipset is by realtek (HD).

    I tried a shorter cable and that seemed to be a little better so I'm thinking the cable might need to be shielded.

    Any ideas? Thanks.
     
  2. seronx

    seronx

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    It might be the power supply and the cable might need to be shielded(With chokes? I think)
     
  3. micropage7

    micropage7

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  4. twilyth Guest

    I have some shielded video cables that should work, but I can't seem to find an adapter to go from 1/8" stereo to RCA. I have a patch cable that does this and that's what's plugged into the extension cable but since that's not shielded, I don't think it will work.

    I noticed that I get the hum even if the cable is unplugged from the computer but not the receiver, so I guess it has to be EMF that is getting picked up and then amplified.

    I know I have a short 5" 1/8th to RCA patch cord some place. If I can't find it I guess I'll hit radio shack tomorrow.

    edit: I just realized that it does sound like that 60hz hum you used to get with analog tv's sometimes.
     
  5. silkstone

    silkstone

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    try some strips of tin foil, that may help shield the cable, and give you an idea if that is the problem or not.
    I've noticed sometimes dodgy connections can cause a hum too.
     
  6. seronx

    seronx

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    twilyth, try going to Digital Outputs instead of Analog Outputs
     
  7. streetfighter 2

    streetfighter 2 New Member

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    Ditto. If your receiver has digital inputs (toslink/spdif) it's insane to use analog.

    Most realtek HD onboards aren't exactly the crème de la crème and the analog output may even have innate noise. By switching to digital, particularly toslink, you can (theoretically) transfer audio lossless to the receiver.
     
    Last edited: Jun 19, 2011
  8. twilyth Guest

    Well, I still get the hum when the cable is unplugged from the pc, but it stops if I unplug from the receiver. I don't think that leaves too much doubt about it coming from the cable.

    I don't have the patience to try to wrap the cable with foil. Plus I would probably screw it up anyway. It would be easier to just get a shielded cable.

    I found my little 1/8th to RCA adapter but the cable I had in mind isn't shielded.

    Does such a thing even exist? I mean, if it's shielded, it has to be grounded, and with an RCA jack, where's the ground? If you can get shielded audio cables, I guess you must have to ground them independently. :confused:

    You know, I always forget about that option since I've been using HDMI for audio. What sort of cable do I need? Is it fiber optic? I'll have to see what I can find online.
     
  9. silkstone

    silkstone

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    i was actually thinking it could be a dodgy connection, but yes, its a pain in the ass and not worth it. i was just brainstorming ideas :)

    found this that may help

    http://ask.metafilter.com/141687/Ho...uter-case-which-I-cannot-take-out-and-replace

    From what i remember about digital audio cables, they are fibre optic. http://en.wikipedia.org/wiki/TOSLINK
    only thing is, i'm not sure how long you can get them.
     
  10. streetfighter 2

    streetfighter 2 New Member

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    Both your motherboard/soundcard and receiver need to support S/PDIF (which they should if they were made in the last 10 years). Are you using the mobo listed in your specs (Biostar TH67+)? If so, sorry for saying it, but your rear I/O sucks. ;)

    Your mobo has an internal S/PDIF header which you can attach to an S/PDIF PCI bracket that will provide for a standard RCA cable (rarely BNC) and/or TOSLINK (an optical cable).

    Apparently it's quite popular to build the aforementioned bracket:
    http://www.avsforum.com/avs-vb/showthread.php?p=13173004

    This should also work if you'd like to avoid the labor:
    http://3btech.net/spoppcibrcot.html (Shows $9 w/ free s/h)
    http://www.amazon.com/dp/B0035J9Z7W/?tag=tec06d-20 (Same as above but more expensive)
    http://www.keenzo.com/showproduct.asp?M=GIGABYTE&ID=933142&ref=GB (Out of stock)

    I get my TOSLINK cables from monoprice though newegg also sells them. I'm sure you have an RCA cable lying around, should you choose that route.
     
    Last edited: Jun 19, 2011
  11. twilyth Guest

    Thanks for looking that stuff up.

    As it turns out, the HTPC happens to be in my specs. Weird. I almost never fill that out and when I do I never update it. But I tend not to rebuild the HTPC as often as the other rigs so maybe that's why I did it that way. IDK.

    I looked at the manual and there is an S/PDIF header but the AV inputs on the receiver that aren't RCA or HDMI are just labeled "optical" so I'm guessing those would be toslink. I did see a few spdif to toslink cables so I assume that would work. IDK. I'll have to look at the receiver manual and see what they say.

    I was really hoping this wouldn't turn into another project, but it is what it is I suppose. :toast:
     
  12. stevednmc

    stevednmc New Member

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    Sounds like a ground loop hum to me. It may be just a bad cable, running to close to AC lines or a bad jack in the receiver. I would go digital for the audio, probably your best bet as mentioned above. Those things can be fun to track down and if your having to splice shielded and unshielded cables together just to make the connection, it isnt worth it imo. The more splices/connections the more signals can degrade and other potential issues.
     
  13. streetfighter 2

    streetfighter 2 New Member

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    When the receiver says "optical" it means "SPDIF via optical". Most receivers have an input section labeled "Digital" and anything in that section will be SPDIF. You could just let us know what model the receiver is though . . . ;)
    SPDIF is just a protocol that can be transmitted either by optical (TOSLINK) or coaxial (RCA/BNC) cable.

    In other words, an "SPDIF to TOSLINK cable", if such a thing exists, probably just converts between optical and coaxial SPDIF (ergo not really helpful).
    It's not nearly that bad. Personally I'd just get the optical/rca bracket for $9, then hook it up RCA or (preferably) TOSLINK to the receiver.

    If you're technically inept then it could take an hour. Seeing as how you're quite technical I don't see the whole process taking you more than 10 minutes, with the majority of the time being spent getting the HTPC unplugged and open and making sure the wiring is correct.

    The result is no more hum and better sound.
     
    Last edited: Jun 19, 2011
  14. twilyth Guest

    The receiver is a yamaha htr-5063 (the other one is an rx v765 and has more options)

    Both of the inputs look like all of the other optical ports I've ever seen - little black door over the port. I'm not sure if this is what you mean by "RCA" but for me, that means something like a banana plug except shorter and with ring of metal around it.
    [​IMG]
    The optical jacks definitely aren't RCA.

    They look like this
    [​IMG]

    That's why I was talking about some sort of adapter cable.
     
  15. twilyth Guest

    You know, none of this would be a problem if I could just run the hdmi through the receiver, but then I can't set the HDTV up as a second monitor to span the desk top. In fact, I don't think the tv registers at all when I do that.

    But that sort of makes sense if the tv is passing identity and config info back to the card (which is an ati 5850, not nvidia - that was the old HTPC). You would think the receiver would pass that info along, but I guess not.
     
  16. streetfighter 2

    streetfighter 2 New Member

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    On the HTR-5063, AV-1, AV-2, AV-3 and AV-4 all support SPDIF. AV-1 and AV-4 support SPDIF via TOSLINK (optical) and AV-2 and AV-3 support it via RCA (coax) (the orange jacks). I'm colorblind so if they're not orange then I can tell you they're definitely NOT white/red/yellow/blue/green :roll:.
    [​IMG]
    :roll: Yeah, you got that right :slap:
    It has an internal header, just no bracket. I linked him to one for $9.
    [​IMG]
    I'm not crazy . . . I'm not crazy . . . Repeating myself makes this true . . . Repeating myself makes this true . . .
    :roll:
     
    Last edited: Jun 19, 2011
    hat says thanks.
  17. hat

    hat Maximum Overclocker

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    It looks like your motherboard has an HDMI port... maybe the onboard audio chipset has provisioning to use that for audio? Connect that to any of your receiver's inputs with an HDMI cable. There might be something in your audio drivers about using that HDMI port for audio. It looks like up to this point we've been steering you in the wrong direction, as it appears your board has neither optical or coaxial S/PDIF. Your only option is trying that HDMI port (which, if it works, would be the best solution anyway), buying a sound card which does support this sort of feature, or sticking with the analog.

    Here's his board for reference:

    BIOSTAR TH67+ LGA 1155 Intel H67 HDMI SATA 6Gb/s U...

    //I'm glad I picked up this knowledge for myself here on these forums. I truly am an audiophile, even though I'm using Altec Lansing 45.2s right now over traditional stereo analog...
     
    Crunching for Team TPU
  18. hat

    hat Maximum Overclocker

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    Does it? Impressive... I didn't know. Is it that 3 pin header there at the bottom of the board? Wow... so does mine! I never knew... is this a common/standard feature? Would your onboard audio drivers handle this?
     
    Crunching for Team TPU
  19. Sinzia

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    I've never seen a board in years that didn't have a SPID/F header on it somewhere.
     
    hat says thanks.
  20. twilyth Guest

    You see, this is problem you have dealing with someone who's too stupid to know what they don't know. I never even noticed the different colors. And obviously I know less than nothing about digital audio protocols.

    Now I'm beginning to see how this would actually be pretty simple to do with a bracket and the right plug for the header.

    While we're here though, what sort of cable do I need for the orange RCA jacks. Are all RCA cables coax by definition? If so, then I guess the outer conducter would act as the ground.

    Thanks for all your help btw.

    HDMI is already being used to feed video to the tv. It also feeds audio, but then I'd either have to use the audio out jacks on the back of the tv to feed the receiver or I'd have to settle for the tv's internal speakers.

    edit:Oh, and the onboard video is disabled. I had been using it but then went with the 5850 instead.
     
  21. streetfighter 2

    streetfighter 2 New Member

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    God I hope not. The brackets are stupidly hard to find unless you want to build one yourself. (See my earlier post for details.)
    I have no reason to believe otherwise.
    Damn straight. :laugh:
    Despite what Sinzia says I've used any number of different RCA cables, pulled from the 50 or 60 miles of different RCA cables I have (slight exaggeration implied :D), and as far as I can recall they all worked.
    For the love of god: monoprice.com :laugh:
    The wikipedia page seems to indicate "75Ω coaxial cable". I'm not sure why it needs to be as nice as an HDTV coax cable. I believe RG6/U is the standard, not RG6-QS; but any 75Ω coax should do it including RG59U.

    Check it out:
    http://www.monoprice.com/products/search.asp?keyword=spdif&x=0&y=0
     
    Last edited: Jun 19, 2011
  22. Sinzia

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    That digital cable is usualy cable TV cable with RCA's on it, ususaly RG6-QS.
    Its -not- the same as standard RCAs, they just use the same connector, in the same way that CAT6 cable is not the same as CAT5, even tho it still uses the same RG45 connectors.
     
  23. twilyth Guest

    Ah. Good to know. what would I search for on someplace like newegg? when I looked for spdif all of the connectors looked like mini-stereo plugs.
     
  24. Jetster

    Jetster

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    Why not use the HDMI sound as its intended to be used. If yur runnig a HDMI cable to your TV then run an optical to your receiver from your TV. Under control panel switch to HDMI sound
     
  25. twilyth Guest

    I tried to explain this upstream. The HDTV is the second monitor on my HTPC. I'm running the HDMI to the tv but don't want to use the internal tv speakers.

    I can't run the hdmi through the receiver since when I do, the HDTV doesn't register any input. Some part of the signal is getting stripped out by the receiver (just a guess). Either that, or the HDMI protocol supported by my old Sony KDS-50A2000 is the problem. IDK.

    So my options are
    a) run digital audio from the HTPC to the receiver or
    b) use the audio out jacks on the tv to feed one of the AV inputs on the receiver.

    I'm going to check into option b tomorrow and see if that helps. If not, then I'll get one of the brackets street pointed me to. :toast:
     

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