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Zoom G3 and ground noise..


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  • Zoom G3 and ground noise..

    Bought  Zoom G3 and am having issues with ground noise. Both of my guitars when hooked up to Mustang 1 do not have this problem.

    I like the G3 but as of now It is useless for recording.When Im on batteries its fine but when I use other means of power,USB,wallwart, it buzz's ike mad.And even on batteries when I hook up USB to record it buzzs. I have to use laptop battery for buzz to go away.

    This is quick clip of noise  I recorder in Reaper. First few seconds are all battery powered.Laptop and G3. You can hear when I plug power back to laptop. Then I touch guitar bridge which does make it slightly quieter but not much.

    Bad unit or just crappy house wiring??

    Sound clip..Im using a high gain amp with no noise gate.


  • #2

    If my guitar is anywhere near my laptop the pickups hear the laptop and the Zoom G3X goes crazy.  You can hear this in the beginning of most of my recordings where I press play and then walk away from the laptop.

    Signature is here!


    • #3

      There are multiple symptoms here; from the descriptions it sounds like the G3 is susceptible to just about all the common sources of noise:

      • Bad power supply rejection (susceptible to its own power supply noise when on AC).
      • Ground loops: noise varies with connections to other equipment.
      • Bad common mode rejection on the guitar input (noise responds to changes in capacitive connections between human body and guitar hardware).

      That's what might happen when a box is made by designers whose main expertise is digital.

      Here is a test of G3 designer competence. Open the thing up and find out whether the cable shield ground from the guitar jack goes to the circuit board (incorrect) or whether the ground is separately routed all the way to a common ground point near the power supply (correct: avoids the dreaded "pin 1 problem").  (I don't want to bring up the term "chassis ground", because the thing looks like it's made of plastic.

      Also try the ground lift.  I see from photos on the net that it has a ground lift switch on the rear panel.

      That doesn't address all hum problems, but see what, if any, difference it makes in your various scenarios.


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      • #4

        You need to use a zero hum adaptor like a Boss or a Danelectro. They only cost about $10 and will fix the problem.

        Most generic type wall warts are piss poor for filtering the DC voltage. You wind up getting AC ripple injected into the circuit which is what causes the signal to hum. Its not a ground issue its a bad DC voltage that isn't smoothed properly.  


        • stratotak
          stratotak commented
          Editing a comment

          Ill have to look into getting a better power adapter. I like the unit but first the hum and then when I tried to ignore it I find out I get popping and crackling when I record.Adjusting latency didnt help.Its a old laptop with a P4 at 1.8 ghz running Reaper and cpu is only around 6-10% when recording.So its not CPU load.To get rid of it I had to uninstall G3 asio drivers and use asio4all. Sucks when a generic wrapper works better then manufactures drivers specifically written for the G3.

          Also wondering If a bad worn outlet could cause the hum. Have a outlet that I have to bend the prongs slightly outward for plugs to stay in. I need to replace the outlet. Could a worn out outlet cause something like that and effect the ground on other outlets to??

        • Kazinator
          Kazinator commented
          Editing a comment

          Are you using this with the original factory power supply?

          If so, it is probably this one:


          From the label, I can tell that this is a switching power supply, because it runs on any voltage from 100 to 240V.

          This type of supply puts out a regulated DC voltage.  The DC voltage has ripple, but the ripple has a small amplitude, and is at the switching frequency (above the audio range, maybe some 30 kHz or more.)

      • #5

        I have the same issue with mine.  It does seem to be a ground kind of problem, but not a 60-cycle-hum problem.  It's related to using the same power supply on two units in the same chain, I think.

        Scenario:  I have two Zoom G3X units.  I'm trying to run one into another, in series.

        It results in LOTS of high-pitched noise.

        If I power just one of the two units from my power supply, the noise is present, but very very soft.  It can be completely eliminated with very conservative settings of the noise reduction.

        If I run two units in parallel, the second unit in series has the same noise, but VERY VERY loud.  NO amount of cutting this signal out from the first unit, using EQ or noise reduction, will help very much.  It's not just the result of amplifying the soft noise from the first unit; this noise occurrs even if both units are in bypass.

        If you press buttons on either G3X, the noise will change slightly.  If you've ever heard radio interference from a computer, it's like that;  memory accesses and changes to the screens will cause changes in the sound.

        So it seems like a ground issue.  If you are powering a G3-style unit from the same non-isolated power tap as anything else in your chain, you risk this noise.  And two Zoom-brand devices in the same chain powerd thus, can result in HIDEOUS noise.

        I'm powering both units from a 9V battery supply, with no switchmode power supply in it--just a NiMH battery pack.

        I'm going to try solving this using separate battery packs for each G3X unit,  But I need some adapters to make that happen.


        • Kazinator
          Kazinator commented
          Editing a comment

          kozmikyak wrote:

          Scenario:  I have two Zoom G3X units.  I'm trying to run one into another, in series.

          It results in LOTS of high-pitched noise.

          These symptoms point to bad design. It sounds as if the PCB traces and ground planes on the GX3's circuit board are not properly laid out to protect the analog side from digitial noise. Also, if the input and output jacks are likely grounded to the circuit board rather than to the chassis, then you have a "pin 1 problem". Under the "pin 1 problem", jack ground hookups act as antennae, bringing cable shield noise into the circuit board, so that it traverses a maze of sensitive circuits before findings its way off the circuit board again and to the power supply ground.