Noise from USB connections UA-1g and RD 300GX

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mcdos
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2011/05/23 07:48:19 (permalink)

Noise from USB connections UA-1g and RD 300GX

Ok, so I have a UA-1G and a Roland RD-300GX keyboard connected together so that I can record the output from the keyboard using the UA-1G. That all works fine until I try to hook up the Keyboard to Sonar via its USB connector and then I get low level, but noticable high pitched noise coming through the UA-1g which is noticable on the recording.
 
If Sonar is not fired up the whole setup works fine, but as soon as Sonar is up, the noise returns. Removing the USB lead from the keyboard kills the noise too.
 
So I reckon there is a high frequency ground loop issue here and maybe nither the UA-1G or the keyboard isolates itself from the ground of the computer and the result is this noise. Anyone know of any fixes for this? Perhaps a galvanic isolator for the usb lead will work, but the only ones I've seen so far are silly money and I don't need 4kV isolation!
 
I tried a ground loop isolator on the signal path (keyboard to UA-1g) and that had an effect, but didn't eliminate it and thats another £75 for an incomplete solution.
regards
steve
#1

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    Billaboard
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    Re:Noise from USB connections UA-1g and RD 300GX 2011/05/23 15:55:48 (permalink)
    When I looked into this sort of thing wrt laptops and usb devices, I ended up sorting out power supplies (and also used some audio isolating transformers that I reclaimed from some old electronics.

    I did have two websites bookmarked

    http://microcontrollersho...D&products_id=3769

    http://www.circuitsathome...surements/usb-isolator

    But decided that it was all too difficult. The second one seems to describe something that does usb2, the first just usb 1.

    Some of my usb cables have ferrite rf blocks at both ends. They didn't help here, but you never know.



    #2
    mcdos
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    Re:Noise from USB connections UA-1g and RD 300GX 2011/05/24 03:18:20 (permalink)
    Thanks for that, I had spotted those two on my we search, they appear to be the right sort of product, but are both appear a bit "home made" if that doesn't seem too rude. I may have to give one a try, but I'm wondering why no one has developed a mass produced item that does the same job? I've seen a few posts round and about relating to similar issues with noise from USB, so I suspect its perhaps more of a common issue? 
     
    I tried my local music gear shop and they could only offer conventional analogu ground lift kit.
    Cheers Steve
    #3
    Billaboard
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    Re:Noise from USB connections UA-1g and RD 300GX 2011/05/24 06:43:18 (permalink)
    I was really hoping that someone would try the second of these and report back. If you plough through their confusing websites you can find that a built and tested version costs $48.

    I don't do anything that needs this sort of thing anymore, but I do think there's a gap in the market just waiting for someone in China to step in. It has always been difficult to find decent, cheap isolating devices, none noisy power supplies for laptops and so on.

    Hope you find a decent answer soon,  Bill
    #4
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