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Noise interference.

Discussion in 'Sound City' started by Dempsey22, Aug 23, 2018.

  1. Dempsey22

    Hitman

    Joined: Nov 5, 2013

    Posts: 909

    Location: Ireland

    Okay so I got my new speakers yesterday. JBL LSR305s.

    I have them connected like the following.

    PC > Modi 2 > Magni 3 > LSRs

    I have an annoying noise coming from both speakers that gets more high pitched when CPU is under load. If i disconnect USB that connects the Modi 2 to PC then sound is gone.

    What is the most affordable way to solve this?

    Optical out isn't an option as I dont have the Modi 2 Uber.

    Thanks
     
    Last edited: Aug 23, 2018
  2. Marsman

    Capodecina

    Joined: Oct 18, 2009

    Posts: 10,161

    Hmm. This could be an issue, as it would seem you have electrically noisy USB.

    Do you hear the same noise if using headphones with the Magni?
     
  3. EsaT

    Mobster

    Joined: Jun 6, 2008

    Posts: 4,159

    Location: Finland

    You could try USB isolator.
     
  4. Dempsey22

    Hitman

    Joined: Nov 5, 2013

    Posts: 909

    Location: Ireland

    Im at work till tomorrow so will check then but I cant remember if it was with the headphones.

    When I use my headset and mic through the back audio ports I did get same noise through that headset. It only went away when I plugged them into the front audio.

    Ill try use the front USB port for the Modi 2 and see if it makes a difference.

    Schiit recommended a powered usb hub or else their Schiit Wyrd but for 110 quid its abit steep.
     
    Last edited: Aug 23, 2018
  5. PapaLazaru

    Capodecina

    Joined: Dec 23, 2009

    Posts: 16,989

    Are you using a USB directly connected to the motherboard?

    *edit* Sorry did not read.

    Are you plugging it into a USB 3? If so, try one of the old ones. My Marantz HD-DAC1 does not like USB3 either.
     
  6. Dempsey22

    Hitman

    Joined: Nov 5, 2013

    Posts: 909

    Location: Ireland

    Was in USB 3 but switched to USB 2 made no difference.

    I tried all remaining USB ports and same.

    Next option is to try an external powered USB.
     
  7. Mick-1965

    Wise Guy

    Joined: Nov 19, 2007

    Posts: 1,081

    Location: Leicester, UK

    Sounds like an earth loop problem.
    Your pc is connected to the earth via its own 3 pin plug.
    You've just added a powered speaker at the end of your audio chain which also has a 3 pin plug directly to the mains which creates a loop.
    So now your PC can now try and earth through the loop via your speaker at the end causing noise on the earth which is what your speakers are picking up.
    You can test to see if it is a earth loop problem by plugging the speakers into an extension lead, but in the plug of the extension lead temporarily remove the earth wire.
    If the noise stops take steps to break the earth loop. As above a usb isolator or a RCA phono isolator between the magni and speakers.

    Under no circumstances run the speakers permanently from the extension lead with out the earth.
     
  8. Dempsey22

    Hitman

    Joined: Nov 5, 2013

    Posts: 909

    Location: Ireland

    Absolutely spot on. I had a 3 pin to 2 pin adapter lying next to the computer. Just popped that onto extension lead and plugged it into socket. Powered back on speaker and no noise from it whatsoever :)

    What will be the easiest option for both speakers? The USB isolator or the RCA isolator? I seen the USB ones are 1500v and 3000kv. Which would I need ?
     
  9. Mick-1965

    Wise Guy

    Joined: Nov 19, 2007

    Posts: 1,081

    Location: Leicester, UK

    The isolator should simply isolate one side of the loop from the other. Other words breaking the earth loop.
    As long as it does this either should suffice.

    Rca phono isolators seem to be your cheapest option.
     
  10. Dempsey22

    Hitman

    Joined: Nov 5, 2013

    Posts: 909

    Location: Ireland

    Ordered an RCA isolator. Will be with me next week.

    Thanks again for your help.