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Type: Posts; User: John Reynolds

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    Hi, When you look at the schematic and PCB...

    Hi,

    When you look at the schematic and PCB layout for the Audio Shield, there is a ferrite and two caps connected to the VDDA input pin on the IC. Removing the ferrite disconnects the VDDA pin...
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    Hi Chip, The part your arrow points to is indeed...

    Hi Chip, The part your arrow points to is indeed the ferrite. I did exactly what you are describing and it dramatically reduced the noise! I built a linear supply and connected it across the VDDA...
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    I used the Bass Preamp at a gig this weekend and...

    I used the Bass Preamp at a gig this weekend and it worked pretty well. The power supply noise is essentially gone - now there's no more background noise than with any other guitar/bass rig I'd...
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    Thanks for posting the simulations! I was aware...

    Thanks for posting the simulations! I was aware of the LF roll-off issue. When I picked the 0.22uF output cap, I thought the pots I had were 25K, but it turned out they were 10K :) When I realized...
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    Here's what I did for the preamp. I used LND150...

    Here's what I did for the preamp. I used LND150 MOSFETs because I've been using them for other experiments - they're good up to 600V :-). Other FETs would probably work fine with some resistor...
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    Bass Preamp Project

    A couple years ago I started working on a bass guitar preamp using a Teensy 4.0 and the Audio Shield. I was able to try lots of different topologies for gain and tone controls and used it on stage...
  7. Does moving the Audio Shield away from the Teensy...

    Does moving the Audio Shield away from the Teensy reduce the noise floor on the audio outputs? Also, would there be any possible noise advantages to running the shield from a seperate 3.3V supply?
    ...
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    Hi Frank, My thinking was that the biquad...

    Hi Frank,

    My thinking was that the biquad object in the library would be the easiest way to implement the first order filter, since its uses a subset of the biquad structure (most of the biquad...
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    Apparently there are lots of ways to calculate...

    Apparently there are lots of ways to calculate coefficients for digital filters! :)

    I found C code examples for a pair of first order filters (thanks Google!) that also seem to be working fine. ...
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    First Order Filters

    I've been experimenting with first order filters for a bass preamp. I've been able to get a Low Pass filter working just fine by calculating the coefficients with this code:


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