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Laptop to Amplifier

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  • 11-09-2003 3:39pm
    #1
    Eglinton
    Closed Accounts Posts: 992 ✭✭✭


    I want to connect my laptop to my guitar amplifier so i can play music through it without the hassle of changing cd's etc. I have tried this by connecting the phono-out socket to the input of the Amp. This works fine on batteries. But when the laptop is connected to the mains there is huge interference. I know that there is power going in both directions and it may be bad to connect to the phono socket. I have a TV out port so maybe I could connect thru this? But I also want to be able to connect to the TV for music visualisations.Any advice?


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    #2
    MartinHSabag
    Closed Accounts Posts: 186 ✭✭MartinHSabag


    Hi Eglinton
    There is no power going hrough that connection.
    The TV out delivers only video out so it doesn't help you either.

    The interfierence you are getting (Hum ?) is probably due to a ground loop

    Read the link about it and how to solve it.


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    #3
    milltown
    Registered Users Posts: 4,616 ✭✭✭milltown


    I have used my laptop on numerous occasions as a mobile jukebox by connecting the 3.5mm headphone output to a pair of phono inputs on the mixer, I think I've used a 7mm jack before too.
    Quality will depend very much on the laptops audio chip and on the hardware of the headphone socket. Fortunately mine is sweet.


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    #4
    Eglinton
    Closed Accounts Posts: 992 ✭✭✭Eglinton


    I'd say its grounding problems alright.They're on separtate plugs. I'll try it and let you know. The soundcard is good and the laptop has excellent altec lansing speakers. But they don't deliver enough power for parties obviously.Everything is fine till its on the mains.


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    #5
    Eglinton
    Closed Accounts Posts: 992 ✭✭✭Eglinton


    Still doesn't work right. Tried going off the same socket with the same ground.


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    #6
    Eglinton
    Closed Accounts Posts: 992 ✭✭✭Eglinton


    Anyone else have suggestions?


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    #7
    LeperKing
    Registered Users Posts: 451 ✭✭LeperKing


    Are you actually sending the laptop out to the guitar input? Because that would never work properly. The guitar input is of high impedance, and your laptop output is low impedance. You shouldn't expect good results trying to do that!

    LK


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    #8
    Eglinton
    Closed Accounts Posts: 992 ✭✭✭Eglinton


    It doesn't actually make a difference which input i put it in. Its fine while the laptop is on batteries but once its on the mains it buzzes away.


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    #9
    Eglinton
    Closed Accounts Posts: 992 ✭✭✭Eglinton


    I really want to use the laptop as a jukebox soon so any help on the matter would be greatly appreciated.


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    #10
    MartinHSabag
    Closed Accounts Posts: 186 ✭✭MartinHSabag


    Why won't you buy an external sound card (USB) and get over with it ?


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    #11
    Eglinton
    Closed Accounts Posts: 992 ✭✭✭Eglinton


    Sound. How much do they usually cost?


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    #12
    MartinHSabag
    Closed Accounts Posts: 186 ✭✭MartinHSabag


    here is one chepo one and you can go for a really good one like this


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    #13
    ZENER
    Registered Users Posts: 6,163 ✭✭✭ZENER


    You could also try the Griffin iMic. I have a couple of these lying around if you're interested.

    Also with regards to the noise. I doubt this is a ground loop problem. Nearly all modern laptops use a switched mode charger/psu which have no connection to mains earth and use a two wire mains cable. Also the mains side is isolated from the output side of things.
    I think guitar pickups are low impedence (600 - 1K ohms) similar to mics.
    Does the output on your laptop have a headphone logo on it's audio out socket? What sort of pitch is this noise ? Do you still get the noise if it's plugged into a proper line input on an amplifier ?

    Tinky


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    #14
    Eglinton
    Closed Accounts Posts: 992 ✭✭✭Eglinton


    Yes the laptop has a headphone logo on it. The noise is quite high-pitched but there is a lot of distortion also. Only happens when connected to mains. Could it be a conflict with the amp itself


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    #15
    ZENER
    Registered Users Posts: 6,163 ✭✭✭ZENER


    Have you tried connecting to a standard line input of say a hi-fi amp ? Is the noise still present ?

    I don't really have an answer to the high pitched noise but perhaps a suggestion to what might be causing it. Many modern notebooks use some form of power management features of the CPU and peripherals. Powering the machine from mains may turn the CPU to full speed thus increasing the possibility of poor s/n ratio by introducing digital noise to ground. It;s also possible that under battery power the amplifier that drives the headphones may be throttled back to a low (line level) output instead of a higher low impeadence output level. This may be the reason a guitar pickup input that normally takes 3 - 10 mV at 600 ohms could take the line out of the pc on battery power which would be attenuated when going into such a low impedence when its expecting something in the order of 10K to 50K ohms.

    Tinky


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