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Ground loop buzz between blackbox and bluebox when powered from the same power bank

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  • Ground loop buzz between blackbox and bluebox when powered from the same power bank

    I guess I'm lucky to never have run into serious ground loop buzz issues before, so maybe this is nothing blackbox/bluebox specific, but looking for advice nonetheless.

    Traced the issue to this:

    Plugging blackbox (any of the outputs) into bluebox (any of the inputs) with a short (<1m) 3.5mm to 3.5mm stereo cable (tried several cables that work fine elsewhere) generates a loud buzz if they're powered from the same source. Suspected the wall-powered USB hub with no ground pin at first, but the same buzz happens if both boxes are plugged into a USB power bank (Anker PowerCore 20100 mAh).

    Didn't know it was possible to get ground loop buzz from a power bank! Or is something else going on here?

    What are the options for portable power specifically? Do I need a better power bank (any recommendations?), or one of those "ground loop noise isolator" gadgets on the audio cable?

    Thanks for any tips or pointers!

  • #2
    A ground loop isolator would definitely help, but I am actually choosing to power my Blackbox and Bluebox from separate power banks (using the smaller Anker units so that they fit in the case with the respective unit). Powering USB powered devices from the same source is a ground noise nightmare, so I keep them separate (and my NTS-1). It is easier for me to manage then plugging in a bunch of USB isolators.


    • #3
      Reporting back with some findings, as I got a couple of gadgets to try addressing the issue. I have a very limited understanding of electrical engineering concepts, so just looking for ready-made solutions online and trying them out.

      1) USB charger with a ground pin (this particular brand was recommended on some audio forums..)

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      DOES NOT resolve the issue, high frequency buzz is still present if I plug both blackbox and bluebox into it. It's a nice sturdy box tho.

      2) Audio Ground Loop Noise Isolator:

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      IT WORKS! Running the audio cable between blackbox and bluebox through this removes the noise! After a quick check, I'm surprised how well it works. The filter itself is light and not too obtrusive, and has 3.5mm jacks on both ends so you can use your own cables. I wish the jacks were a bit "tighter", it's a bit too easy to yank the cable out, but overall not the worst solution.

      (I got these two different ones and there are a few other options in the $10-15 range. I can't tell if there's a difference in the sound quality between these two, they both work quite well)

      Also ordered one of the cheap "USB Isolator Modules" to try, but hasn't arrived yet, will post once I try it.

      Bonus link from my "research".. should I be using a Black Box to power my blackbox?
      Last edited by IgsterKicks; 02-25-2021, 02:32 PM.


      • #4
        3) GeeekPi USB isolator module (cheapest "usb isolator" on Amazon):

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        DOES NOT WORK AT ALL. Neither blackbox nor bluebox are able to draw power through this piece of crap.
        Last edited by IgsterKicks; 02-25-2021, 02:24 PM.


        • #5
          you need a device that provides 2a and those are not cheap, being more $$$ than bluebox or blackbox. most isolators only isolate data connections not power. theres a couple cheapish designs from ‘hifime diy’ that provide up to 400ma but this isnt enough for bluebox.


          • #6
            Does anyone have specific recommendations for a usb charging station with isolated ports that provides enough power?

            And separately, it's still not clear to me if a portable solution (with a single power bank) exists? The audio isolator works, but I'd like to run three audio cables between blackbox and bluebox, and feels like a hassle to isolate each, if the problem can be resolved with the power supply.


            • #7
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              this thing is amazing, does the same thing as the usb isolator at a much cheaper price! im impressed, thanks for the heads up!

              click image for amazom page


              • #8
                Glad the audio isolator works for you too Solipsvs !

                So I tested a couple more things:

                4) A fancier version of the USB isolator - iFi iDefender+

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                DOES NOT WORK in this scenario. I plugged one of the boxes via this, and the other straight into the shared power source (tried both the USB hub and the power bank). Buzz buzz.

                5) Clip-on ferrite filters on the audio cable (hell I tried them on the USB power cable too)

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                DOES NOT WORK in this scenario. Buzz buzz.

                6) An "industrial grade" USB hub with a dedicated DC power adapter:

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                DOES NOT WORK in this scenario. Buzz buzz.

                I think I'm done for now. For desktop use, I replaced my USB hub with a simple power strip and I am powering blackbox and bluebox through their individual USB power adapters. This also seems to be a common wisdom in the various audiophile forums -- use individual power adapters.

                For the on-the-go portable scenario I guess the simplest option is to duct tape a couple of individual power banks together

                Or use the audio isolator.

                Or maybe use one of those large power banks that provide AC power, and then plug multiple USB power adapters into it? I have not tested this.

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                • #9
                  Hi all, i'm experiencing the same buzzing when connecting the Black Box to the Blue Box. Just as IgsterKicks I have tried various solutions to avoid the crazy buzzing that kicks in as soon as both devices are powered on. TBH I'm a bit surprised by this when none of the Blue Box videos on Youtube seem to have this issue.

                  I have an Elektron Overhub that I wanted to use to power the Blue Box, Black Box and 4 Roland Boutiques. In this setup I have to turn the volume to somewhere between -30 to -40 dB to kill the buzzing.

                  I have tried various power sources without it making much of a difference.

                  I have an OmniCharge (71Wh, [email protected]) but that doesn't make a difference. Not even with the two devices connected to two different power sources

                  I'd be interested in knowing if there are some default settings for volume and/or gain that id recommended for new projects that could help eliminate some of the buzzing or maybe specific types of cables or just power connections that are known to be better..?

                  // Morten


                  • #10
                    Oh, one thing I should probably make more specific is that:
                    1. Blue Box on one power supply and the Black Box on another works. No buzz.

                    2. Blue Box and Black Box on same power supply (usb hub) results in buzzing. Seems consistent regardless of the type of power is used (usb hub, power bank, etc.).

                    3. Blue Box on one isolated Power supply, and Black Box + one more Device (ie. Roland TB-03) on another power supply results in buzzing. If one of the two devices on the other power supply is disconnected the buzzing goes away.

                    4. Blue Box with Black Box and Roland TB-03 connected, and all devices connected to separate power sources (3 different usb hubs) works = no buzzing.

                    Hope this makes sense to someone at 1010music
                    Would be great not having to have individual usb power sources for each device connected to the Blue Box


                    • #11
                      I bought this ground isolator

                      it works perfectly !!!