1. A proposal is now up as a poll to change the guidelines of TGP to only allow member self-deleting of post/threads for up to thirty days of the original posting it. We are now watching the poll here. Click here to view the thread.

    Dismiss Notice

HD USB hummmmmmmm...

Discussion in 'Digital & Modeling Gear' started by sevser, May 22, 2011.

  1. sevser

    sevser Member

    Messages:
    49
    Joined:
    Oct 25, 2010
    Location:
    he Okanagan Valley in BC Canada
    Whats up with this hum??? Everything else works great...

    Its not my pups, or the monitor. It doesn't even matter if my guitar is plugged in.

    Any ideas?
     
  2. guitarnet70

    guitarnet70 Member

    Messages:
    2,900
    Joined:
    Oct 25, 2010
    Ground loop? Try plugging the HD on a different socket than the computer (and the monitors). Try also another USB port on your PC.
     
  3. sevser

    sevser Member

    Messages:
    49
    Joined:
    Oct 25, 2010
    Location:
    he Okanagan Valley in BC Canada
    I happens as soon as I plug into the PC. Through my PA its fine.
     
  4. guitarnet70

    guitarnet70 Member

    Messages:
    2,900
    Joined:
    Oct 25, 2010
    Then is something with your pc. Have you tried other usb connections? It could be some kind of interference with the fans in the case...
     
  5. s0c9

    s0c9 Member

    Messages:
    302
    Joined:
    Dec 26, 2010
    Location:
    USA
    is it a laptop or a desktop ?
    Laptop power supplies are notorious for causing audio hum. If laptop, run it on battery for audio.. then switch back to power when done.
     
  6. JJ321

    JJ321 Member

    Messages:
    1,347
    Joined:
    Jun 6, 2007
    Location:
    NG, Maine
    If it's a laptop, try unplugging the laptop and running it off batteries. My old Dell hummed like crazy as soon as I plugged the HD500 into it. When I unplugged the laptop and ran it off batteries, it would stop.
     
  7. KozMcCharlie

    KozMcCharlie Member

    Messages:
    200
    Joined:
    Oct 6, 2008
    Location:
    In the hills of Jersey
    My 500 hums when it is close to the LCD monitor, but much less when moved 3' away. I picked up a USB extension of 8' and it's pretty much silent. Also I can use it on the floor now.
     
  8. 1wheel

    1wheel Member

    Messages:
    315
    Joined:
    Jan 23, 2009
    Location:
    Cincinnati, OH
    All,
    Some thoughts on the Hum issue.. (this will put you to sleep)..

    The first place to look for hum would be the different grounding locations of the PC and HD (though the HD floats from the AC line).. The PA may not be floating relative to the AC ground, and the USB shield/ground would connect the PC to the PA ground via the HD... that makes a possible ground loop... It is not USB per se, just the shield grounding the system.. Plugging all elements into the SAME AC outlet (or UPS) would minimize this.

    A secondary source of Hum in audio is like our single coil pickups. Any signal cable that makes a large physical loop (shield and center conductor combined) can pick up magnetic fields (like from AC power in your house, transformer magnetic leakage, etc.) and that current will induce a small voltage into the cable loop (it is really just like a leaky transformer or magnetic guitar pickup). To reduce this, make the loop as small in area by keeping cables in a line vs a big open shape. An example of this is AC power cables like lamp cord, the wires are closely parallel and as a result, there is not alot of magnetic leakage (same with normal IEC AC cables, they are twisted internally but not shielded).

    Lastly, is device generated magnetic leakage. A good example is a laptop charger (and perhaps the HD AC power adapter). These devices use high frequency switching converters that operate at 200kHz to perhaps 1.5MHz. The are very leaky and do generate significant magnetic noise. All of this is above our hearing, but the energy is modulated at 60/120 Hz rate as the AC voltage and charging current follows the AC input. The modulation of this high frequency noise is what we often hear in our audio gear.

    In general, keeping systems plugged into a common AC ground point is a good thing. Keeping cables from being in large loops helps and AC adapters need to be as far from gear as practical. Magnetic fields drop in level very quickly, so separation makes a big difference..

    On the personal experience side, I have never had any hum issues with my HD500 (other than pickup issues in guitars).
     
  9. jrockbridge

    jrockbridge Member

    Messages:
    3,944
    Joined:
    Sep 29, 2008
    Location:
    Above Ground
    I was able to solve the ground loop problem on 2 laptops, by using those orange plug converters that you can find at a hardware store. Both laptops have a 3 prong electrical outlet plug for the ac/dc adapter (power supply). The orange plugs are 2 prong male to 3 prong female adapters intended for allowing 3 prong plugs to be used in very old houses. But, the orange plugs will work as an earth ground lift in a typical home...just do NOT attach the earth ground part to the socket screw.

    You can also buy a Hum-X and it will reduce the hum. They are kind of expensive and only eliminate about 80% of the hum noise in my experience.
     
  10. sevser

    sevser Member

    Messages:
    49
    Joined:
    Oct 25, 2010
    Location:
    he Okanagan Valley in BC Canada
    Thanks 1wheel...I'll try the common ground!

    Its a desktop PC...It does this as soon as I even touch the USB cable to the USB inputs housing. Not the guitar, because I don't even have to have it connected. (IT IS LOUD!

    I tried every other USB in my PC...1wheel may have hit it in the head!

    THANKS PEOPLE!!! :D
     
  11. 1wheel

    1wheel Member

    Messages:
    315
    Joined:
    Jan 23, 2009
    Location:
    Cincinnati, OH
    Sevser,
    I'm a bit concerned about your AC wiring or a device in the signal chain..

    My concern is that you may have something in the PC/Laptop or PA that is causing the ground of that 'element' to be offset from earth ground. Note that tube guitar amplifiers (with 2 prong cords, like my CBS Fender DR... 1980) have a switch that has 3 positions, A, none, B. What that is really doing is 'picking' a side of the 2 prong cord to 'believe' is the neutral (the side of a 110V line that is grounded to the center of the 110/neutral/110 line transformer on the pole). One side is called line (the 110V from ground) and the other 'neutral' should be near or at ground.

    If you choose poorly, the tube amp 'ground' will be floating 20 or more volts (with very low current) above ground. You get 'zapped' by microphones/elbows on mic stands, etc.

    It seems that either your laptop charger (Dell and Sony have 3 prong AC cords on laptop supplies) may have alot of leakage that is not maintained near ground. It is also possible that something else is causing leakage into the wall plug ground (and this might be dangerous).. It very well could be that your AC plug (on the wall) is not properly grounded..

    They have wiring testers at Lowes/Home Depot (Canadian equivalent ?), that will show a bad ground... Or have an electrican check the ground for continuity.

    This seems too big of a leakage to be just cable routing...

    Write up your actual configuration or PM me..
     
  12. sevser

    sevser Member

    Messages:
    49
    Joined:
    Oct 25, 2010
    Location:
    he Okanagan Valley in BC Canada
    I plug into my mixer from out of the 500...and thats into a powered monitor. (They are using the same outlet) Then the USB into my desktop. (The 500 and the PC are plugged into the same outlet)
     
  13. 1wheel

    1wheel Member

    Messages:
    315
    Joined:
    Jan 23, 2009
    Location:
    Cincinnati, OH
    Suggest this:

    Test 1:
    Unplug the HD outputs from the mixer and listen with headphones connected to the HD for hum (the assessment goal is to see if the level of hum changes relative to the guitar signal, and yours is significant hum from you comments)

    Test 1 result: Hum is essentially gone
    This means the Mixer or Monitor is forcing the HD signal ground off of earth ground. Go to test 2

    Test 1 result: Hum remains
    This means that the HD power supply is leaking AC into the HD signal ground (the AC/DC plug converter has a leakage path that might be significant).. try a different HD supply (warranty issue?). you could try flipping the supply in the outlet, but the supply should not leak that much current to the signal ground. End of test (report back)

    Test 2:
    Plug the mixer into the HD via the XLRs as you have at the start but disconnect the monitor(s) from the mixer. keep the headphones connected to the HD for now.

    Test 2 result: Hum is essentially gone
    This means the mixer is likley NOT the culprit. verify by putting your headphones in the mixer and checking for hum. go to test 3.

    Test 2 result: Hum returns
    This means that the mixer is pushing current into the signal ground. for a floating mixer (non IEC cord into back panel), the AC/DC wall adapter (or brick supply) may be defective. If the mixer is grounded with an IEC cord, then there may be internal issues in the mixer. Report back.. end of test

    Test 3:
    Connect the monitor(s) to the mixer

    Test 3 result: Hum is essentially gone
    Then I'm lost, we are back to the starting configuration but hum went away... report back.

    Test 3 result: Hum returns
    Then the monitor is pushing current into the signal ground. try different monitors or a guitar amp (a bad suggestion for this hum chase).. report back

    I re-wrote this a few times trying to make this logically better.. In my case, I really have NO hum in my PC desktop/HD500-USB/Mixer(Yamaha O1x)/PA configuration. Others have indicated some hum.. your hum must be quite bad.

    Let us know how the testing went..

    Thanks,
    Pete
     
  14. sevser

    sevser Member

    Messages:
    49
    Joined:
    Oct 25, 2010
    Location:
    he Okanagan Valley in BC Canada
    Dude...YOU ROCK! I will test er out when I get home! :)
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice