Just noise with Teensy 3.6 and Audio Adaptor Board

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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?

I experimented with a Teensy (4.0?) and Audio Shield a couple years ago and always had some background noise I could never get rid of -- I was using it as a preamp/tone control for my bass guitar rig. I tried opamp buffers on the input and outputs, but that didn't get rid of the noise.

I ended up repurposing that hardware for something else (Solfeggio Tone Genator :) but I'm thinking about taking another run at the Bass Preamp design.

Just wondering if anyone has some ideas for improving the performance of the Audio Shield for this application :)
 
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?

There should be a definite noise reduction if using a separate, linearly regulated, analog supply on any ADC or DAC for audio -
digital supplies for a high speed CPU are typically attrociously noisy from DC to many GHz. A single CLC filter is not going to
really do enough, although its doing a lot of good I suspect.

Although you should certainly get benefit from using a separate analog supply, the Audio shield doesn't bring out the analog supply,
so you'd have to desolder the ferrite bead and connect to that pad. The audio shield ground layout may not be ideal though, so this might
have limited effect if there is ground noise injection to the audio inputs or outputs, and their might be inappropriately positioned
decoupling caps injecting digital rail noise into the wrong part of the ground net too.

If you do contrive a separate 3.3V analog supply it should be coupled to the digital 3.3V supply with back-to-back schottky diodes to
prevent internal phantom powering - most mixed signal chips require the two supplies to be simultaneously present, back-to-back
diodes enforce this until both regulators have settled.
 
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