Noise when playing bass through USB interface

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rms13
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Noise when playing bass through USB interface

Post by rms13 »

My set up:

Debian Wheezy running Jack audio and Guitarix or Rakarrack
Focusrite Scarlette 2i2
$20 Sony MDRZX100 headphones
Muscian's Gear gold tipped instrument cable

When I have everything plugged in and set up I hear a constant feedback/ground/humming kind of noise. When I play the bass it's not as bad but it is still present. I can't get a clean signal. I was using a cheap $10 usb interface so I bought the Focusrite to replace it figuring that was the weakest link in my chain. But now I'm having the same problem. I just want to use my computer as a virtual practice rig for my bass. Any suggestions? All of my gear is brand new so I doubt it's something failing but who knows

Jarle
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Re: Noise when playing bass through USB interface

Post by Jarle »

Try with another electrical outlet; so the USB-soundcard and computer is connected to different electric lines - to see if that solves the problem. If you are not using headphones; check where the amplifier is connected to. I had similar and solved it by reorder where I connect the equipment to mains (used an extension cord witch I connected to different outlet in the house to find out witch who interfered with each-other, for troubleshooting).

Eino
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Re: Noise when playing bass through USB interface

Post by Eino »

If it is a low 60hz tone you are getting, it could be a polarity issue between equipment.
"Music is everybody's possession. It's only publishers who think that people own it. "
John Lennon

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rms13
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Re: Noise when playing bass through USB interface

Post by rms13 »

Thanks for the suggestions. The usb interface is bus powered so it is not plugged into any AC power source. My computer is a laptop and I get the noise even running off battery only. So I'm guessing that rules out ground loops.

How can I troubleshoot the polarity?

artek
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Re: Noise when playing bass through USB interface

Post by artek »

rms13 wrote:When I have everything plugged in and set up I hear a constant feedback/ground/humming kind of noise.
Can you post noise file?
Do you hear this noise with only interface connected to laptop running on batteries?
I would also check interface on other computer... but it seems to that your laptop is source of noise.

Eino
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Re: Noise when playing bass through USB interface

Post by Eino »

rms13 wrote: How can I troubleshoot the polarity?
You really can't with out a volt-om meter, But you can try switching out usb cables with different ones.
Could be a problem with a leaky shield on a cable.
"Music is everybody's possession. It's only publishers who think that people own it. "
John Lennon

https://soundcloud.com/eino1953

rms13
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Re: Noise when playing bass through USB interface

Post by rms13 »

I guess I hadn't tested with the laptop unplugged. I unplugged the laptop power and the sound is much clearer. Not 100% clean but better

Jarle
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Re: Noise when playing bass through USB interface

Post by Jarle »

Does your USB cable have ferrite isolation? if not try one that does have isolation (small cylinder near usually both ends).

artek
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Re: Noise when playing bass through USB interface

Post by artek »

I guess I hadn't tested with the laptop unplugged. I unplugged the laptop power and the sound is much clearer. Not 100% clean but better
Does your USB cable have ferrite isolation? if not try one that does have isolation (small cylinder near usually both ends).
ferrite wont help on power line hum, but should suppress rf noise
I would give try to something like that http://electronics-shop.dk/?id=1038 USB 2.0 Isolated - Galvanically isolated USB 2.0 Full Speed Adaptor

artek
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Re: Noise when playing bass through USB interface

Post by artek »

man, even Tiffany have her laptop unplugged on official scarlet video
http://www.youtube.com/embed/dCu8gZc1nOE :lol: :lol: :lol:

bazsound
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Re: Noise when playing bass through USB interface

Post by bazsound »

If you have access to a DI, try that and lift the ground. It might further reduce the noise. Depending on what the noise is. Ground Loops can be tedious to trace. but the solutions others have posted are valid. Trying different power sources can often reduce noise problems. Sometimes the ground can get disconected in a 4 way adapter. I make a point of checking these from time to time as its a dangerous fault. And can also cause noise in some cases.

But it is quite commen to have noise issues with some laptops when connected to a powersuppy. Sometimes a better power supply can fix.

What kind of bass are you using? ive also had times this happen on certain instruments. When the tone control was adjusted one way you would get a terrible buzz. could be related to poor sheilding in the instrument or just poor wiring.

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