How to solve a ground loop?

    Good evening,

    I'm struggling with a bad ground loop (I think).


    When I've my Kemper plugged into my Focusrite 2i4 I can hear a noise, expecially with high gain profiles, which is directly linked to the movements of my mouse and even when my CPU is working more intensively.

    I've tried to push the ground/lift button both in the Kemper and on my speaker (FRFR108) but it hadn't any effect.

    I can hear that noise even with the headphones directly connected to the Kemper.

    I've tried also to move the Kemper in a separate current outlet but it was useless.

    The only way to stop this is to unplug the USB audio interface. So I think the issue is coming from the USB connection that it should be causing a ground loop.
    But I'm quite confused, because I've kept the Kemper connected to the same motherboard to use RigManager and no noise can be heard.

    So, should I have to change my audio interface because it is defective or should I have to investigate more (e.g. on the PSU of my PC, which is mid-range one)?

    Has anyone win this battle with similar problems?

    Many thanks!


    Does it disappear if you unplug your guitar ?

    Is your mouse wireless ?

    I don´t think it´s a ground loop issue ( hum @ approx 50 - 60 Hz and @ 100 - 120 Hz )

    more likely some electrical interference from ( mouse ? ) VGA screen, computer PSU,

    dimmers , WIFI or whatever electric gadgets surrounding your workplace .... :/


    Cheers !

    The adjective for metal is metallic. But not so for iron ... which is ironic.

    When the Kemper is off I can hear the noise through the FRFR 108, because I have one of its input connected to the Kemper and the other to the audio interface for listening also the PC audio when I need. As Ipreviously stated, the only way to eliminate the noise is to disconnect the Focusrite 2i4 from the USB cable (which is is power source).

    If the kemper is on and I unplug the cable or engage the kill switch of my guitar the noise is attenuated.

    My mouse and keyboard are combo wireless, one adapter for both.

    I have LCD IPS screen

    For the PSU, here is my doubt. I've tried to put it out of my PC case but nothing is changed.

    Since it is a good 550W plus gold certified power supply which has almost 4 years of normal/light usage, I prefer do not change it unless I would 100% sure that it is the origin of the problem. I have no graphic card because I use the one integrated in my i7-6700 CPU so I think is well sized for my deskpo PC.

    I'll wait for some advices or opinion!

    Many thanks.

    When the audiointerface is usb powered you get all kind of noise from your pc. This is a known issue with bus-powered usb connections. The only way to solve this is to isolate the usb power. There are some usb isolators out there, but they may slow down the whole thing and provide to little power for the interface.


    Something like the "ifi iDefender3.0" works, but you need an additional external power supply. Usually a low noise LINEAR 5v power supply is best. They are hard to find or pretty expensive nowadays. You can try other 5v power supplies, but you will probably catch new / other noises with them.

    Low noise SWITCHING power supplies with filters can be quiet too, but often "contaminate" the setup with noise in the other direction - so other devices in the power strip are suffering.

    Have you tried to unplug "everything" and then put it together

    one piece at the time in different order to determine witch

    item starts the noice ? :/

    And keep at least one item (KPA) grounded all the time !

    Safety first ! =O


    Cheers !

    The adjective for metal is metallic. But not so for iron ... which is ironic.

    Quote from Wheresthedug

    As ibot39 said, it is a ground loop caused by the USB output. You can buy isolated USB cables which should solve it.

    It's not ground loops alone, I think. The problem is, that the usb cable does transfer very "dirty" 5V (usually red colour positive wire) from the pc to the audiointerface, which you only hear when running the Kemper connected to that interface or a (gainy) amp sim. Caring about ground loops and turning down the preamp on the interface does help a bit.


    But for best result you need isolated or separate, clean 5V power for the interface in addition. This has the biggest effect in reducing /eleminating this kind of noises.


    I don't know about a single usb-cable that can do all this by itself?!

    I don't think that usb connection from pc to Kemper is a problem in THIS case. The main problem here is the bus powered usb connection from pc to audiointerface.


    For other cases there are cheap usb isolators available. For example I use such cheap china adapters for connecting my nux solid studio (for editor) to eleminate any noise the unit generates.

    Quote from Wheresthedug

    Yes, I used to have the same issue with my RJM Mastermind PBC connected to the editor by USB. Apparently there is an isolated USB cable that sorts it. I never bought one as I ended up just unplugging the USB from the PBC but it is likely to be more useful leaving the KPA connected.

    Many thanks for your reply! I think that this isolated USB cable could be a solution for me. Do you know a commercial cable of this kind?
    I would like to have the audio interface on while I'm playng with the Kemper so I have to find something like this if I want to solve the problem.
    Thanks again!

    Quote from Ibot39

    I don't think that usb connection from pc to Kemper is a problem in THIS case. The main problem here is the bus powered usb connection from pc to audiointerface.


    For other cases there are cheap usb isolators available. For example I use such cheap china adapters for connecting my nux solid studio (for editor) to eleminate any noise the unit generates.

    Thanks for your reply! Do you advice me an USB isolated cable and do you know a commercial one I can buy?
    Thanks again!

    What came to my mind: For the mouse, you can try setting a lower polling rate (if this is supported) or try another mouse. I had problems with a wired mouse too.


    As said, the main problem is the usb connection from pc to interface. You can try something cheap (search for "usb isolator 1500v ADUM4160"), but you'll need an external power supply for your interface. And this will probably SLOW down your usb or maybe will not work at all.


    What does work for me is the mentioned "iFi iDefender3.0". It does break the usb supply voltage - that is the most important thing!! But it does not slow down anything.


    For a powered device like your interface you still need an external low noise power supply.


    Or you look at something like this power supply:

    http://www.aqvox.de/usb-power_en.html

    One of the versions (I think) also does break the usb supply voltage, but I am not sure.


    I use the iDefender in addition with an aqvox power supply with micro usb connection. Not a cheap solution at all, sorry. But it was the only thing that worked for me.

    Many thanks for your reply!

    I just have to clear my mind a little: My focusrite 2i4 snd gen has just one USB type B port which serves both as data transfer and power supply. In your opinion, to solve the problem can I just apply the iFi iDefender3.0 at my motherboard's USB port and from here connect the data/power USB cable to my focusrite?

    Many thanks.

    Yes exactly.


    The iDefender3.0 will break the power supply line, so the interface no longer gets power from the usb/pc. Data still gets through unaffected, full speed.


    You need an external 5v power supply with micro usb, that you connect to the side of the iDefender.

    But with most switching power adapters you'll get annoying noises. So you should use linear 5v or low noise adapters with good filters.

    Many thanks, again!

    Can you advice me some specific 5V power supply? I have the 5V 1A charger of my old iPhone, but I don't know if it would be suitable as low noise for this application.

    If you buy this for example, you will not need the iDefender:

    http://www.aqvox.de/usb-power_en.html


    "It is equipped with unique handmade USB adaptors, of which one side is being pluged to the USB socket of the DAC or device or computer and the back side takes the USB cable´s plug. Inside that adapter only the two USB data lines and not the powerline are routed through. The 5 V power supply line coming from the computer is terminated and replaced by the clean power of the AQVOX USB-Low-Noise power supply."


    If you want to use the iDefender3.0, there also is a AQVOX power supply with micro usb plug.


    I have these, but the price for all this stuff is pretty high. They change a few parts like the plug, but it is basically a rebranded cheap 20 dollar made in taiwan ac adapter. I think the brand was called "zip". But nowadays hard to find.


    You can look at ebay for (old/used) made in taiwan or china linear adapters with 5V DC 1A output. But they don't have the right plug (micro usb) for the iDefender. Or you try the iFi iPower 5v adapter that is available in a set with the iDefender. But as said, I am not a big fan of switching power supplies, for the above mentioned reasons. But maybe it works in your setup. If not, send it back.


    The iPhone charger will probably introduce more/other unwanted noise - but you can try this of course.


    I get the best result with the iDefender (breaks earth and usb power) combined with the AQVOX adapter with simple micro usb.


    If we are talking about the same issues this will completely kill the noise. If you find another solution or adapter, let me know.

    Edited 2 times, last by Ibot39 ().

    Thanks for your reply!

    Just to let you understand what I'm exactly talking about I report this video:

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    I exactly hear the same noise, sincronized with my PC working activity (e.g. mouse movements). However,. the content of the video is irrelevant for our discussion.

    I've read the aqvox article and I founded it really interesting: it also includes some interfaces that are compatible, but only the Scarlett 2i2 is reported for Focusrite brand (maybe because 2i4 requires more power since has more input/output ports?).

    Also, I haven't seen any price or order form. Do you know how much it costs?

    So far, the iFi iDefender seems a good solution, but I have to find a proper 5V power supply.

    I've also founded another interesting point of view: If one connects the internal chassis of the Focusrite through an electrical wire to the case of the PC that provides the feed, the ground loop could be broke as a new lower impedance path for the current that generates the noise is created.

    Altough seems the cheapest solution to try I haven't yet, because I'm not really excited at the idea to open it but, by by logical point of view I think it could be a working solution.

    Don't know why the TAG didn't work! Sorry, the upper post is a reply to your latest one. Many thanks.