USB Ground Loop Noise Eliminated!
ByHappy New Year Everyone!,
If you play the electric guitar, sooner or later you will have to deal with ground loop noise. As your guitar rig grows, so does the potential for unwanted noises & hums in your system. The upside to having noise problems is learning how to deal with them. I’ve found that dealing with noise problems requires more imagination & creativity than technical knowledge.
As for ground loops, the rule of thumb is, do not have multiple grounding sources (i.e- Don’t plug your amp into one wall socket and your pedal board into another wall socket – plug them into the same power source with the same ground.)
If you have noise coming from an individual pedal, chances are the pedal is not receiving the correct amperage. The voltage might be fine but your power supply may not have enough amperage.
Another noise problem can arise when a line cable is too close to a power source.
Gear companies design their equipment to “see” grounding sources in vastly different ways. That usually leaves us asking the Heavenly Father for guidance in putting “quiet” rigs together.
Today, I was working on eliminating a ground loop noise coming from a USB cable plugged into a Mac G5 and a Korg X50 keyboard. The noise sounded like digital jibber-jabber combined with a high pitched whine.
When I unplugged the USB cable, the noise disappeared. I needed the Korg X50 on the USB port for MIDI and patch editing purposes. Unplugging the USB cable to track keyboard parts was not an option.
After looking at different internet sites, forums and blogs, I took a shot at a creative solution. I had to sacrifice 2 USB cables but, the problem was eventually solved.
In the middle of the USB cable, I stripped away a section of the rubber coating to expose a 1/2 inch of the braided shielding. I then cut the shielding entirely away exposing the 4 wires in the middle. I made sure the shield was completely disconnected by testing for contact (continuity) on the opposite metal ends of the cable. I then proceeded to cut the “black” wire that supplies a ground source through the USB cable via pin #4.
After the surgery, I plugged the altered USB cable between the Korg X50 and the Mac and “voila”, no more high pitched jibber-jabber.
Another ground loop bites the dust!
11 Comments
February 13th, 2009 at 1:44 pm
Thank you so much for publishing this little nugget of wisdom. I have been tearing my hair out for days trying to get rid of exactly what you have described. I have just bought a Waldorf blofeld (excellent synth fyi)and it only has a midi in port and so depends on usb for two way transfer. This is my 1st bit of kit that is like this and so have not encountered this horrible noise interference before. You have just restored my noise floor back to the way I like it, very low. Thanks again
June 16th, 2009 at 6:44 pm
Hi. I like the way you write. Will you post some more articles?
May 10th, 2010 at 9:16 am
if you are going to use third party USB cables, makes sure that they have the RU or UL mark for best performance.*~*
November 4th, 2010 at 3:34 pm
most cheap USB Cables are not very durable and it can cause errors in data transfers too ”
November 14th, 2010 at 4:54 am
Hey Man, its midnight and if it not were for you i would be pulling an all nighter trying to figure how to fix the ground loop. This is awesome you saved me a couple of hundred dollars in DI boxes for my keyboard and a few others in a new computer… and the midi signal still there… I was afraid I was gonna lose sync but it seems that everything is OK even without that ground line… which i assume is pure digital and at some point in the path does something nasty with the usb bus in my computer… even when i moved the mouse i added another hum….I guess i still need a better DAW but now everything is decently clean and I can move on and work on my music.
Thanks a lot for this post!!!
December 3rd, 2010 at 8:12 pm
you can always tell the quality of USB cables by looking at the thickness of the cable. thicker usb cables have higher quality :”`
December 12th, 2010 at 12:38 am
I tried this, at first the usb device (a Digitech GSP1101) wasn’t recognised and didn’t see the USB connection.
It turns out that you have to leave the black wire connected!
For me the hum wen’t away with just the outer shielding cut away and the black wire still there..
This could have something to do with the fact that at the ports, the pins are connected to the circuit board, and the shield is connected to the casing.
Ultimately the board and case lead to the same ground, but apparently not perfectly..
So, try it with just the shielding cut first, you can always still cut the black wire if it doesn’t work.
December 12th, 2010 at 8:03 am
It just goes to show that all devices have different ground configurations.
March 30th, 2011 at 2:41 am
I know this thread is old, but cutting the ground wire worked for me too, but is it safe to run electronics without the usb ground?
March 30th, 2011 at 7:15 am
Remember, the problem was caused too many ground sources. Just do not use your altered USB cable on any other peripherals.
January 1st, 2012 at 3:56 am
I had similar problems with a Boss DR-880 drum machine hooked up to a Digi002 console running Pro Tools 8. Audio out of the DR-880 was clean & hum free until I connected a USB cable to the DR-880 to slave it off the MIDI clock from Pro Tools. At that point the hum from the analogue outs on the DR-880 made any recordings un-usable. I immediately suspected an earth loop and seeing that I never had hum problems before I decided to use the DR-880 USB port, that became suspect number 1. Disconnecting the USB cable confirmed this but left me with the problem of not being able to slave the DR-880 via USB MIDI. I tried the method above by disconnecting the earth screen and cutting the internal black earth wire. It did get rid of the hum but the PC then refused to recognise the DR-880. On a hunch, I re-connected the internal black earth wire but still left the screen cut. The PC now recognised the DR-880 and everything is working fine without any hum. Because the data being sent along the USB is only slow speed MIDI data, I can’t see any problems with interference but using tis method may cause issues trying to send multichannel audio via an audio USB interface.