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USB hum
I'm getting crazy. I have a hum that disappears when I touch one of my devices, e.g. the iPad. The funny thing is that I have only digitally connected gear via USB. I've got an audio interface but usually I have nothing plugged into its audio inputs or outputs. The hum also happens on the iPad audio jack. When running off the battery the hum is gone. My usual setup
- iPad with Apple CCK
- Powered USB hub from IceBox
- iConnectAudio 2+ audio interface
- Launchpad X
- Korg nanoKeys Studio
- All audio devices plugged to the same power strip and other stuff like lamps unplugged (normally plugged into the second main socket at my desk)
I spent already some hours to plug everything out and back in again. Even if I just have my iConnect audio device plugged in, I hear the hum. What can I do?
- DI-Box? Why, I have no analog gear
- Groundlift Cable? For iPad and audio interface?
Comments
Have you tried powering your peripherals with a powerbank? The hum could be coming from the mains.
I've experienced two different types of hum: mains hum which can be fixed by using battery power instead of mains power, and radio interference which is more like a buzzing sound which is fixed by using (expensive) shielded cables. The proliferation of mobile phones and Wi-Fi etc make interference much more of a problem than it used to be.
These things can be such an incredible pain to track down. Have you looked at the spectrum of the hum? It can help to narrow things down.
It could be something injecting noise into the power or the ground. I have had some issues in the past that have been handled by using a USB cable with a choke on it. It could be something coupling RF to the ground via the box of a device.
I've had a couple of cases where different ground levels on different circuits caused issues. It doesn't sound like that's the case here, but it could be. Even though you have everything going through the same power strip, some circuits may only be running on battery and they aren't referencing the same ground level.
Does it happen if you don’t send power to your CCK? In my home, sending power to my CCK via the lightning connector results in hum if the ultimate source is AC power. Putting ground-lifts on everything made no difference. Sending power to the CCK from a battery resulted in no hum.
I also have hum with specific mic and CCK3 via AC adapter, using powerbank fixes it too.
@krassmann I suspect you may have crossed grounds, most likely on the power side. When you touch the iPad case, you ground it and correct the problem. You could try reversing (turning around) the plugs in the power strip one at a time. Or, since you have a powered hub, can you switch more devices to bus power? I assume the power strip is grounded at the wall outlet, and hope the outlet is correctly wired.
Brusfri
Connect everything up and remove each item one at a time. See if you can identify which one causes the issue. If it doesn't occur with battery use, it has to be one of the items powered by AC current.
I am using this power source from Furman www.furmanpower.com ( not sure if this is the solution) but i can say after I started using those, the overall noise( monitors) is considerably lower.
Aren't the factory cables with iConnect devices notoriously unreliable? Would also be interesting to know if the OP is powering it through the USB hub or using the optional power adapter.
And you may need to extent this plugging and unplugging to anything in your house that is on the same circuit -- not just things in the audio circuit path. I have found that in my house there are sometimes items in the next room (which is on the same circuit) that can influence the hum in my office studio.
True espiegel ( i had that experience too) plus my house has a big ventilation system ( living in the desert)...big huge consumers and tons of circuitry > @espiegel123 said:
Good point. If you can't eliminate it with unplugging each audio-related item, then the good news is that it's somewhere else in the house. The bad news is you have to go find it...
If you are in my house, you night have to unplug the sun. My solar panel inverters put a little bit of misshaped sin wave on the mains that causes noise with some devices.
@krassmann : Apparently this is common enough an issue to require it’s own tech to solve: usb isolators: these people do a cheapish one, and offer an explanation for it:
https://hifimediy.com/product/usb-isolator/
Yes, it only happens when at least one device is connected to mains
Inserting the lightning cable with power creates the hum. But without the powered lightning cable I also get the hum when I connect the USB cable to a device that is connected to mains, like the powered hub. I need this hub as all my USB devices are too much even for the powered iPad.
I'll try turning the plugs. I can try to do everything bus powered. But in the literature it is even advised to use mains instead of bus power to avoid hum. Yes, the strip is grounded and the electricity in my house is not old. I think it's okay.
Yes, that's true. If nothing is connected to mains and everything runs off my power bank then there is no hum
You may find -- like me -- that when you need to be rid of the hum, you have to run off batteries (mine can run my rig for a few hours). So, I live with hum when it doesn't matter too much and switch to my batteries when I record.
I am curious in what literature they suggest running off AC rather than batteries to avoid hum? 20 years ago when I got my first digital multi-track (a zoom recorder) it was well-known that in some environments, the only way to avoid hum was by running on batteries.
Fellow giver-upper here as well. I tried for countless hours in two homes in California to get rid of hum. I tried unplugging everything else in the house, a fancy power isolating plug box, ground loop eliminators and everything else I could think of with no luck. I finally gave up and just use a battery bank when I need to record anything external.
I found it
After two hours of plugging in and out, turning plugs, changing strips, trying other mains, turning fuse off, etc. I found the reason
Drumroll....
My headphones.
Not only one, it happens with two of my headphones and exactly these two I’m using for music making: my €80 Sennheiser IE40 Pro super sounding in-ear monitors and also the Apple EarPods with 3.5mm jack. All other headphones in my household don’t hum. Luckily including my Superlux HD 681, which I also used for music. It’s good but just not so comfortable for long sessions. Even the most cheapos I got as a promotion present don’t hum. Tried the humming headphones on my iPhone and on my son‘s Android phone - humming when powered. So, I’m really sure it’s the headphones.
But anyway it still has to do with power as the hum only occurs when connected to power. Another funny effect: I had the iPad connected only to it’s original power supply and when plugged in one direction it hums, when turned the power supply around it doesn‘t hum. Even more funny with any other USB charger turning around didn’t help, only Apple charger in one direction did not hum.
It’s really mad. I‘ll contact Sennheiser about it and file a support case. Thanks everyone for help. Without all the inspiring ideas I would not find it.
Ping! Just wanted that you know the end of the story, maybe it’s helpful for you, too.
@richardyot @espiegel123 @NeonSilicon @Janosax @uncledave @michael_m @Svetlovska @wim @Sergiu @telecharge
I have a powered usb hub and find that the order in which USB devices are plugged in makes a difference. Sometimes. FIIK why.
It sounds more like a high pitched whine than it does hum though. Somewhat similar to cell phone interference but more constant in amplitude.