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Thread: DC-coupling line out from Teensy Audio Board

  1. #1
    Junior Member
    Join Date
    Jul 2020

    DC-coupling line out from Teensy Audio Board

    I'm working on a hybrid monophonic synthesizer using the Teensy 3.5 and Teensy Audio Board to produce the oscillator waveform and control signals, which then go to an analog filter and VCA.

    I had intended to use one of the two channels of the audio board to produce control voltage for the analog filter cutoff, but I have realized the line outs are AC-coupled and thus unsuitable for relatively slow-changing CV.

    I'm considering just removing the AC-coupling caps from my audio board. It looks like the row of 4 passives between the SGTL5000 and the line in/out header are the coupling caps for the inputs and outputs; would there be any particular problem just removing those and replacing them with jumper wires?

    The SGTL5000 datasheet implies the headphone outs are DC-coupled, so that might be an alternative as well.

  2. #2
    Junior Member
    Join Date
    Mar 2022
    I use ADAU1701 to try some voltage controlled thing. It works well in my experiment.
    On other experiment,
    I tried to connect ADAU1701 to teensy and it works with Teensy as slave.
    ADAU1701 cheap board was used with teensy 4.0.

  3. #3
    Senior Member
    Join Date
    Aug 2013
    I've been running experiments with PJRC PT8211 audio board (stereo I2S 16-bit DAC) replacing the output capacitors with shorting wires. It works beautifully. Good results from DC up to 500 ksamples/second.

    The results are good enough to allow us to move toward an affordable test bench for our 64-channel data acquisition system.

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