HTPC and Rotel RSP1068 Interference / Noise

Discussion in 'Home Entertainment Computers' started by AngelEyes, Apr 24, 2007.

  1. AngelEyes

    AngelEyes
    Well-known Member

    Joined:
    Mar 23, 2004
    Messages:
    10,617
    Products Owned:
    1
    Products Wanted:
    1
    Trophy Points:
    136
    Location:
    Detached from reality
    Ratings:
    +1,635
    Hey chaps, I hope you can help.

    I finally switched from digital coaxial to 7.1 analogue connections between my HTPC and Processor to take advantage of the new sound formats.

    Unfortunately the upgrade has introduced a nasty buzzing sound through the speakers. It does not sound like a normal ground loop hum as it changes all the time, as the PC does something or you move the mouse or whatever the sound changes. It is like you 'hear' the processor or HDD working via the speakers.

    The buzzing continues when switching to another input but stops once the PC is off. I tried running a cable between the PC chassis and the Processor chassis but it was a half arsed attempt and I cannot be sure I really got a good connection, is this worth trying properly or can you suggest anything else?

    Also worth noting, when connecting via anologue to a 'cheap' 5.1 speaker package in my office I have no noise/interference problems.

    Many thanks,

    Adam

    PS I think that the hum was there with the original digital connection but was much quieter, hardly noticable.
     
  2. AngelEyes

    AngelEyes
    Well-known Member

    Joined:
    Mar 23, 2004
    Messages:
    10,617
    Products Owned:
    1
    Products Wanted:
    1
    Trophy Points:
    136
    Location:
    Detached from reality
    Ratings:
    +1,635
    Well I managed to cure the problem by swapping each PC component out until I found the culprit. It turned out unsuprisingly to be the PSU...

    My expensive 600w Seasonic PSU was creating a load of interference. I swapped it with a much older 480w Tagan which included an earth cable which I connected to one of the the Motherboard screws.

    So if you want to be sure of avoiding interference with your HTPC PSU in a mid to high end AV setup, look for a PSU with an earch cable. :smashin:

    Adam
     
  3. drummerjohn

    drummerjohn
    Active Member

    Joined:
    Sep 2, 2001
    Messages:
    2,497
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    66
    Location:
    South Derbyshire
    Ratings:
    +205
    Interesting... that may be of use to me some day.

    Tell me... have you compared the analogue out quality to that of the digital?

    What Soundcard are you using?

    I am using an M-Audio Revo 7.1 and find the analogue outs less harsh than the digital out with my Denon amp.
     
  4. AngelEyes

    AngelEyes
    Well-known Member

    Joined:
    Mar 23, 2004
    Messages:
    10,617
    Products Owned:
    1
    Products Wanted:
    1
    Trophy Points:
    136
    Location:
    Detached from reality
    Ratings:
    +1,635
    Hi,

    I am using a Creative X-FI and I have only really noticed a difference in the higher bitrate HD material like PCM 7.1 etc on some disks. I don't listen to music that much so can't really compare analogue to digital on 'normal' stuff.

    Adam
     
  5. Neeto

    Neeto
    Standard Member

    Joined:
    Dec 27, 2006
    Messages:
    4
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    1
    Ratings:
    +0
    Hi,

    I have the same problem noise varies with activity on the HTPC.

    I'm using an AudioTrak Prodigy 7.1 HiFi card with analog connection to Rotel RMB-1075 power amp.

    I've already swapped the PSU once and it made some difference, I'm starting to suspect to Motherboard.
    Both of the PSUs where high efficiency (i.e. > 80%) and fanless.
    I'm starting to think these fanless jobs have an a problem.

    Any guidance would be really helpful as I'm about to build the second HTPC.

    Thanks,

    Neeto
     
  6. AngelEyes

    AngelEyes
    Well-known Member

    Joined:
    Mar 23, 2004
    Messages:
    10,617
    Products Owned:
    1
    Products Wanted:
    1
    Trophy Points:
    136
    Location:
    Detached from reality
    Ratings:
    +1,635
    Hi Neeto,

    The cheapest way to tell is to make sure the PSU is well grounded to the chassis and the MB. The Tagan I had in another PC came with a ground cable so was ideal in this respect.

    Just get some heavy guage cable, maybe from some spare mains voltage cable and crimp a couple of spade connectors or similiar to each end. Scrape the paint off the PSU around one of the screw mounting holes and screw it in place between the chassis and the PSU. I then screwed the other end beneath a screw that holds my motherboard in place.

    The main thing is to make sure the PSU is in contact with the case.

    I never used a fanless PSU so couldn't comment on the particular characteristics of them. The main differences between the problematic Seasonic and excellent Tagan was that the tagan has all twisted cables to reduce interference and the earth cable I mentioned earlier.

    They may not have made the difference, maybe the Seasonic was just a 'noisy' PSU, i imagine this is a bit hit and miss.

    You could also try running an earth cable between the HTPC chassis and the AMP as it may help.

    The fact that swapping the PSU made a difference points at the PSU IMO. Out of interest why go for a fanless PSU? SOme of the ones I have used with 120mm fans and fanspeed control are as good as silent anyway and help cool the case.

    Adam
     
  7. Neeto

    Neeto
    Standard Member

    Joined:
    Dec 27, 2006
    Messages:
    4
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    1
    Ratings:
    +0
    Thanks for the reply Adam.

    Will try your suggestions on the earth cable next time I have the case open, which will be real-soon-now i.e. as soon as the other household member are out for the day :D

    The PSUs are now 18 months old and where the quitest around before the PSU with the 120mm fans started appearning.
    My theory being, the less moving part the less noise - good in theory, not in practice :(

    I'm going to build a new HTPC to play HD disc using a duo core.
    I think I can try to reuse one of the PSUs to see if I can get it quite. If I can't I guess I'll have to upgrade it - will try the earth lead first!

    Neeto.
     
  8. AngelEyes

    AngelEyes
    Well-known Member

    Joined:
    Mar 23, 2004
    Messages:
    10,617
    Products Owned:
    1
    Products Wanted:
    1
    Trophy Points:
    136
    Location:
    Detached from reality
    Ratings:
    +1,635
    Hi Neeto,

    I have just been experimenting with putting the Seasonic in my old PC and connecting it up to my RSP1068. I was only watching some old home movies but the buzz was gone!!

    Before I put it in I scraped off a lot of the thick paint around the screw areas and any part that would come in contact with the case, in theory providing a good earth with the case.

    Try it and see if it works, a lot less faff than the earth cable but I suspect that would be the best method.

    Adam

    PS. Check out http://www.projecthtpc.co.uk and http://www.projecthtpc.co.uk/forum/

    For some great help on building your new system. It is a new forum but I have had loads of help there.
     

Share This Page

Loading...