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Thread: Teensy Audio SGTL5000: Line Level Input?

  1. #1
    Junior Member
    Join Date
    Jul 2017

    Teensy Audio SGTL5000: Line Level Input?

    Hello there,

    i am currently working on a simple DSP guitar/line effect pedal,
    using Paul's Teensy Audio Adaptor (SGTL5000).

    I've built a schematic for the input/output pre-amp section, but i am not sure about the input/output levels of the audio adaptor board.

    Are the line inputs bipolar? I mean are they centered (+/-) around 0V?
    I've read in the datasheet that the input of the SGTL5000 can accept voltages between ~0V and ~3V.
    So is this not true anymore for the audio adaptor shield when using the Line input? I mean line signals are usually bipolar +/- around 0V, right? So I would have levels from ~ -1.2V to 1.2V.

    I don't want to damage the audio adaptor. Can i put in signals with -1.2V?

    Here is a picture of the schematic:
    there you can see that right before going into the ADC of the SGTL5000, i remove the DC bias.

    Please also comment on the schematic: Will it work this way, is it designed in a stupid way? (it's my first "not super small" circuit actually) If you're wondering about the thing in the lower left corner: Its two opamps buffering a voltage divider and providing double the output current to power the Virtual GND of the other opamps. Found something like this in a forum somewhere...

    Thanks a lot for replying! If it's possible for you to reply even today, I would really appreciate this,
    because i am very short in time and I try to build this circuit in a few hours. Yeah, sorry...

    Anyway, I will be very happy to read any answers,
    Best regards, Jan
    Last edited by najanajan; 07-06-2017 at 05:10 PM.

  2. #2
    Senior Member PaulStoffregen's Avatar
    Join Date
    Nov 2012

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