UPDATE: SOLVED -Interesting pedalboard hum problem - Calling electricians & braniacs!

Discussion in 'Effects, Pedals, Strings & Things' started by olbean, Feb 22, 2012.

  1. olbean

    olbean Member

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    First off, hello everyone - I am new to this forum.

    Now, I use a pretty big pedalboard - and have spent many hours trying to get the best sounds, and lowest noise from everything.

    I use 3 x Voodoo Lab Pedal Power 2 + & a Voodoo Lab Pedal Power Digital, these power everything, and means that every pedal has it's own isolated power source.

    Most of my pedals are in line, but some of them I like to have in a true bypass loop because this helps me switching multiple pedals on or off.

    Previously, I had been having huge problems where audio cables had been picking up hum from my power supplies, and I would have to position them exactly where they didn't hum, I would have less than a millimetre of flexibility. I made a video to show what was happening: http://www.youtube.com/watch?v=QXc0Nh_XMQg



    Today, I was trying to find out what the hell was going on, and I think I may have sussed it - I just need some help from someone brainy.

    I made another video to demonstrate: http://www.youtube.com/watch?v=k6U10XORLMo


    It seems that if the pedals are connected to the send & return of the looper, there is a bad hum - but if my guitar is plugged directly into the input of the first pedal normally in the loop (and through the rest, back to the loop return) there is no hum.

    Could anyone help me out here? I am confident it is different to a ground loop, because every pedal is on an isolated outlet.

    Many thanks
     
    Last edited: Mar 9, 2012
  2. jnepo1

    jnepo1 Silver Supporting Member

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    Welcome. I would definitely check your patch cables to start, as evident in your first video. Are all of your gear plugged into the same wall outlet? Board, amps, etc... I would definitely have them all into the same source, and a power conditioner. The looper can also be a culprit in all of this, but the patch cables is certainly a good place to start.

    Can you post your signal chain? It's hard to determine the signal flow. Thanks
     
  3. olbean

    olbean Member

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    I have tried a much simpler signal flow, and I still have this problem.

    Even with my guitar plugged straight into the Looper input, amp straight into the Looper output, and with a couple of pedals in the loop I get this interference. The hum changes with the positioning of the cables - HOWEVER if I remove the cable from looper send to the first loop pedal, the hum completely disappears. I have tried different patch cables in this position and experienced no change.
     
  4. jnepo1

    jnepo1 Silver Supporting Member

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    It seems the noise stems from the looper then. Check to see if there is a loose connection or bad solder joint in the looper. Having the looper in the loop seems to be the problem.
     
  5. olbean

    olbean Member

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    I thought that, but I have tried two other loopers! It seems like having the pedals in the loop is somewhat amplifying the hum I get from cables being nearby my power supplies! I am completely puzzled by this.

    If I plug my guitar directly through the pedals, I get no hum whatsoever, but when through the loop - the cables pick it up!
     
  6. chervokas

    chervokas Member

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    Sounds like a ground loop turning the system into an antenna for induced noise. Maybe try to plot out all the paths to ground in the problematic signal chain.
     
  7. olbean

    olbean Member

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    Thanks chervokas, how would I go about doing this? Each pedal is powered by a Voodoo Lab Pedal Power so they should all have isolated grounds, & they are chained using Lava solderless cables. I wasn't aware that grounding issues could be so inconsistent. I thought if it was grounding, the hum would be constant until something is unplugged - but as you said - something is definitely just increasing how much noise is picked up - in this case it is when the looper is involved. I should also mention that it makes no difference whether or not the looper is powered or not - all that changes is the LED.
     
  8. zwolf

    zwolf Member

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    I had this exact issue troubleshooting my band mate's pedalboard. No matter what, I got hum from his road rage looper, even when I went guitar>looper>amp. I figured if all loops were disengaged then none of the individual pedals in the loops could have an effect. Then I got I touch with Jeff from road rage and he told me to check each loop. Low and behold, when I disconnected his DMM, the hum disappeared. Jeff explained to me that if there is a loose ground in one of the pedals, it can cause hum even when the loop isn't engaged.

    We still haven't opened the DMM to check for a loose ground, but that pedal is certainly the cause of the hum.

    Maybe I'm not fully understanding the post and it may not be the same thing, but try disconnecting the sends/returns of each loop one by one. It's worth a shot!
     
  9. olbean

    olbean Member

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    zwolf, thanks for your input - but there is no problem when the loop is bypassed - only when it is engaged! The cables between pedals within this loop are picking up hum from power supplies - and it is somehow being amplified. I can get rid of the hum by plugging my guitar into the input of the first pedal IN the loop, rather than to the input of the looper - however this is not a long term solution because this means in bypass mode, I have no guitar signal (because my guitar is plugged in within the loop).

    Hope this makes sense - but it's driving me mad!
     
  10. iggs

    iggs Member

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    Can't help you unfortunately but definitely can sympathize ... just recently I got a Skrydstrup BF2M buffer for my board and it features a send/return loop for pedals with a separate guitar in/amp out and a tuner out. I was really looking forward to using the unit as I read great things about it and would be nice and neat to have a in/out for my pedalboard.

    After hooking everything up I noticed quite a bad hum. After hours of trying to figure it out finally discovered that when I had cables connecting pedals close to the power supply, the hum would be induced.

    With exact same pedals and cable placement, but having an in-line signal path (not running through the BF2M but using a Axess BS-2 at the end) there is no noise whatsoever.

    BF2M on it's own is dead quiet and a fantastic sounding unit, however, with any pedals connected to send/return loop and cables being in close proximity to Voodoo Labs PP2+, significant level of hum is being induced.

    Yeah ... driving me absolutely mad too!
     
  11. olbean

    olbean Member

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    Ahh it's so annoying!

    I also get hum induced further along my 'in line' chain where my rig changes to stereo. Particularly, two cables going from my Strymon Bluesky into my EHX Cathedral seem to be picking up hum from the Voodoo Lab which is just underneath... but there is none when using the pedals in mono - something else which is quite odd.

    Still - I really don't understand why all this hum gets revealed when the only difference in the chain is that these pedals are put between a send & return of a looper rather than straight line from guitar to amp. I have tried different cables, and different loopers. It's making me sad :(
     
  12. jb4674

    jb4674 Member

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    What kind of cables are you using to go stereo?
     
  13. chervokas

    chervokas Member

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    So you're using a stereo rig? Two amps? Sound like you could have multiple ground loops in your chain. You need to draw a picture of the signal chain for yourself showing all the places the signal chain connects to ground and then you need to get that down to a single ground connection. You probably don't want to use a cheater plug to lift the ground on one of your amps for safety reasons so you may need something with a ground lift on the way to the second amp.

    Do you know what a ground loop is and how it produces hum? If not here's a page with some explanation you may find helpful http://www.pedalsnake.com/page.php?id=1113
     
  14. jb4674

    jb4674 Member

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    I'd like to see pics of the entire rig (from where it plugs into the wall down to the effects and cables)
     
  15. olbean

    olbean Member

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    The rig is stereo, BUT for troubleshooting the problems I am having with my bypass looper, I just plugged one amp into the looper's output.

    My two amp setup is hum free as I use an isolated output on a Palmer Y Splitter to one of the amps.

    The majority of my patch cables are Lava solderless cables, - I don't believe the problem to actually be the cables, because all of the hum disappears when the pedals are in line (not in the looper).

    Why would having pedals in a true bypass loop, amplify hum being being up by the cables!?

    I may make another video showing exactly what i'm experiencing
     
  16. chervokas

    chervokas Member

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    I think a diagram of the signal chain and power connection would be a lot more useful than a vid. Seems like there's a ground loop somewhere or a bad ground connection somewhere or a leaky cap somewhere.
     
  17. olbean

    olbean Member

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  18. FLYING V 83

    FLYING V 83 Pedal Trading Guru Silver Supporting Member

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    First thing I noticed is your guitar cable's metal sleeve lying on top of the Lovepedal, and the out cable of the looper touching the Boss pedal.

    You always do it this way, with metal touching metal?

    Other than that, all the time-based effects should use their own wallwarts & not share off the PP2s (yeah yeah, isolated & all that).

    Also noticed the "Home Depot" quality power strip, if that's your source you should improve your power setup.

    Also make sure all power wires cross at 90° angles to patch cords to eliminate interference.
    After that, remove one pedal at a time from the looper until you find the one causing the noise (probably the compressor, I hate those things!)

    All else fails throw an ISP Decimator on the end of the looper and kill it that way.
     
  19. olbean

    olbean Member

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    First thing I noticed is your guitar cable's metal sleeve lying on top of the Lovepedal, and the out cable of the looper touching the Boss pedal.


    You always do it this way, with metal touching metal?


    I don't use anything made by Lovepedal, I assume you mean the EHX Freeze - the guitar cable doesn't normally plug into the looper there, it plugs into the volume pedal, I plugged it straight in for the purposes of the video - but whether it is touching or not, it makes no difference.

    Other than that, all the time-based effects should use their own wallwarts & not share off the PP2s (yeah yeah, isolated & all that).

    I'm not so sure about that.

    Also noticed the "Home Depot" quality power strip, if that's your source you should improve your power setup.

    That power strip is plugged into a Furman Power conditioner, and the wall power actually has nothing to do with the interference i'm getting.

    Also make sure all power wires cross at 90° angles to patch cords to eliminate interference.
    After that, remove one pedal at a time from the looper until you find the one causing the noise (probably the compressor, I hate those things!)


    As you can see in the video, the entire chain of effects can be completely hum free when 'in line', the hum is only introduced when the pedals are put in the loop, and that hum changes depending on the position of the long cable going from the wah up to the moog.

    All else fails throw an ISP Decimator on the end of the looper and kill it that way.

    NEVER!!
     
  20. FLYING V 83

    FLYING V 83 Pedal Trading Guru Silver Supporting Member

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    Sorry, was focusing more on the cables than the pedals.

    Did you try swapping the cable from wah to Moog?

    Other than that I'd say the looper is the problem.

    I run 17 pedals with 5 through a Loooper, all George Ls, use a PP2+, DC Brick & One Spot, have a Decimator on the board & have zero noise issues.

    Good luck with your issues, it can definetely drive one nuts trying to eliminate hum.
     

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