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Thread: Feedback through pa when laptop is plugged in!!! help!!!

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    Red face Feedback through pa when laptop is plugged in!!! help!!!

    Hi i am running a compaq presario c700 and using a programme called serato scratch live.

    I have a rca connection coming from my booth output on my pioneer mixer DJM600 and into my line in,(3.8mm jack)obvioulsy to record and stream live shows

    Now all is fine with the sound and the hardware,i have it all configured correctley,except when my battery starts to die about 2 hours later and i have to plug it in to keep going i get feedback through my PA any soloutions,or help?

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    Re: Feedback through pa when laptop is plugged in!!! help!!!

    try a shielded rca cable?

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    Re: Feedback through pa when laptop is plugged in!!! help!!!

    will that stop the humming sound i get then,because i thought it was the power brick on the charger?

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    Re: Feedback through pa when laptop is plugged in!!! help!!!

    http://www.skratchlounge.com/index.php?showtopic=5172

    Maybe try some of the suggestions on there

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    Re: Feedback through pa when laptop is plugged in!!! help!!!

    Also what Rane say:

    Make sure your turntable's rca cables aren't running across one another and that the SL1 is as far away from any power source as possible.

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    Re: Feedback through pa when laptop is plugged in!!! help!!!


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    Re: Feedback through pa when laptop is plugged in!!! help!!!

    Or get a USB sound card which will give you a cleaner output

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    Re: Feedback through pa when laptop is plugged in!!! help!!!

    Serato runs through a USB (firewire?) soundcard, some people still get a ground loop though

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    Re: Feedback through pa when laptop is plugged in!!! help!!!

    So surely decent speaker cable will fix that? could be cheap connections that side

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    Re: Feedback through pa when laptop is plugged in!!! help!!!

    In most cases you need to work out where it's coming from an run the cable through a ground loop isolator

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    Re: Feedback through pa when laptop is plugged in!!! help!!!

    This isn't feedback - it is almost certainly noise generated by the laptop's power supply. Switched mode PSUs operate at high freque4ncies and generate lots of harmonics which can be picked up by sensitive audio ccts.

    The problem is in determining where the noise is being picked up.

    As a start, you could add a ferite bead t to the laptop's powers supply - this can stop noise on the power supply lines getting into the laptop. However laptops also have internal SMPSUs which may also be causing problems.

    Ideally for audio work you should be using balanced suignal leads (shielded twisted pairs) where the signal is carried on the twisted pair (tthis cancels ourt series mode interference) and the screening is grounded - and only the screening. (This cuts out common mode interference)

    Alternatively you cn use a balun (balunced to unbalamced transformer) to provide isolation between the laptop and the mixer. You will need two - one at each end of the line.

    Sadly, low end audio equipment doesn't usually have balanced signal inputs - so you are stuck with what you have.

    You can mitigate this by using high quality screened cable (this refers to the quality of the screening - nothing to do with gold plated plugs and other bling) and ensuring that you have eliminated earth loops - ideally all screens should be earthed at one common point and/or by using the balun solution.

    Unfortunately it can all be a bit hit and miss, and until you try various solutions, you won't know what (if any) will work.
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    Re: Feedback through pa when laptop is plugged in!!! help!!!

    i have all the best connections,but like you said it's just noise generated by the power supply,i think i'm gonna go for the easy option and just switch to using my imac for the live out and serato use,it seems much better,ive had a bellend full of laptops,but thank you for your valuable advice!

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    Re: Feedback through pa when laptop is plugged in!!! help!!!

    it's not the transmitting audio that is a problem that is of the highest quality and the actually hmmm from the laptop does not actually come across that bad amidst the music! it's just annoy that's it there,hear it or not

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    Re: Feedback through pa when laptop is plugged in!!! help!!!


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    Re: Feedback through pa when laptop is plugged in!!! help!!!

    does it still make the noise when the laptops not charging, ie battery removed ?

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    Re: Feedback through pa when laptop is plugged in!!! help!!!

    no unplugged it's fine,but as soon as i plug it in, shhhazammm the noise comes

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