Designing a Custom 2-In/2-Out Teensy 4.1 Audio Interface with Hardware Preamp & DSP for Livestreaming

[kimera]

Hi everyone,

I am looking to design and build a custom DIY Audio Interface based on the Teensy 4.1 for my electronics lab setup. My primary goal is to use it for Facebook Live broadcasting, but I also want to incorporate some lab test functionalities.

Here are my specific requirements and what I am trying to achieve:

1. Audio Input & Livestreaming (Priority):

• I use a standard Dynamic Microphone (not a condenser mic). I need to design a proper analog microphone preamp circuit (using low-noise Op-Amps like NE5532 or similar) before feeding the signal into the Teensy Audio System to keep the noise floor as low as possible.
• The Teensy will act as a USB Audio Interface, sending the processed audio straight to the PC for streaming.
• I want to implement Real-time DSP using the Teensy Audio Library, specifically for: Noise Gate (to cut down lab ambient noise), Dynamic Range Compressor, and Equalizer (EQ). I want the final audio quality to be significantly cleaner and more controlled than plugging directly into a PC soundcard or using a basic analog mixer.

2. Channel Expansion (For Future/Guests):

• For the initial prototype, a 2-In / 2-Out configuration is fine (one for my mic, and another Line-In for background audio or instruments).
• However, I would love some advice on how to scale this to 4 channels in the future to accommodate a second mic for a guest and extra stereo line inputs. Which multi-channel Codec ICs would you recommend for Teensy 4.1 that play nice with the Audio Library?

3. Lab Bench Functionality if can (Amplifier Testing):

• I design and build my own DIY Class-AB and Class-D audio amplifiers. I want to use Teensy's internal synth objects to generate precise Sine waves, Square waves, and Frequency Sweeps to test these amplifiers.
• Ideally, I would love to implement an automated Frequency Response and Phase Shift Tracker using the Teensy's inputs to analyze the amplifier's output profile.
• My Dilemma: Since Class-D amplifiers inherently generate high-frequency switching noise (EMI), should I isolate this Lab Bench functionality into a completely separate hardware build? Or is it viable to suppress the noise and share the same Teensy 4.1 platform with my low-noise livestreaming microphone setup without compromising the mic's noise floor?

My Questions for the Community:

1. Are there any existing open-source hardware reference designs or schematics (like T-DSP or similar projects) that I should look into for the analog front-end (Mic Preamp + Codec integration)?
2. What is the recommended Codec choice for a low-noise floor if I want to expand beyond 2 channels later?
3. Are there any known pitfalls when using the AudioEffectDynamics (for Compressor/Gate) alongside USB Audio output on Teensy 4.1?

I would appreciate any guidance, schematic suggestions, or software tips to get this project started.

Thank you!