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UNPLANNED DOWNTIME: 12th Oct 23:45

XLR on USB interface question

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MartinBushMartinBush Frets: 211
in Studio & Recording
A simple question you may thing I should know the answer to, but I don't :)

I have a stereo audio output from a keyboard - quite how stereo it is I don't know, but the output is a stereo jack.

If I want to run this into my USB audio interface would a 3.5mm jack to single XLR be correct? And would it be stereo?

It's not massively important for the keyboard, but I was thinking if I wanted to digitise a cassette it would be.


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Comments

  • Danny1969Danny1969 Frets: 9752
    No
    If you do that it won't be stereo and worse than that only the outer left and right will be left of the signal. The centre will be cancelled. 
    This is because a balanced XLR input is a differential input ... it amplifies the difference between the signal on pins 2 and 3 which are out of phase with each other like a mirror image. 

    You need a special cable really  ... because you need to combine the ring and tip of the 3.5mm to keep all the signal of the stereo image but I wouldn't recommend just shorting them together as this can damage some headphone outputs. 



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  • Danny1969Danny1969 Frets: 9752
    Short pin 1 of the XRL to pin 3 of the XRL
    The sleeve  of the 3.5 stereo needs to go to pin 1 of the XLR

    Put a lowish value resistor in series with both the ring and tip of the 3.5 stereo, bout 16 Ohm  and connect both resistors to   pin 2 of the XRL
    This will combine the stereo image to mono and convert the balanced input to single ended 

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  • mrkbmrkb Frets: 5594
    MartinBush said:

    I have a stereo audio output from a keyboard - quite how stereo it is I don't know, but the output is a stereo jack.

    Are you sure its stereo - the jack you mention is called a TRS jack - which can be used for stereo output or can be used for balanced mono output. The manual should state which it is wired up for.

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  • MartinBushMartinBush Frets: 211
    Thanks chaps. The keyboard is labelled as "stereo", but the principle applies if I was to say walkman.

    The other way to do this would be stereo 3.5mm to two mono 1/4in jacks I suppose.
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  • Danny1969Danny1969 Frets: 9752
    If it's 3.5mm then it's designed as a headphone / stereo line out

    Yes if your interface has 2 inputs then 3.5mm stereo to 2 jacks is ideal.  The cable I described above was assuming your interface only had one input. 
    www.2020studios.co.uk 
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  • MartinBushMartinBush Frets: 211
    Thanks @Danny1969 it has two inputs which, now I think, are probably mono. However your earlier posts have helped me understand a few XLR things in a way other online resources haven't!
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  • Danny1969Danny1969 Frets: 9752
    Ah so you can use the 2 mono inputs as a left and right and record a stereo wav .... in your DAW you can  create a stereo track and it automatically use the 2 inputs and pan them hard left and right to create a stereo wav from the keyboard or tape recorder etc. 
    www.2020studios.co.uk 
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