Recording audio generated by Teensy 4

R

RandomizeUsr

Member
Hello,

sorry if the question was obviuous, but I am wondeing which would be the way to record audio autogenerated by teensy in two different cases:

- When working with the audio shield
- When working directly under usb audio

I mean, record with the own teensy ("autoRecord").

Thanks in advance.
 
If you are recording the digital signal (via USB on your computer or to SD card from the Teensy) the signal is technically the same. In practice it can become tricky about noise depending on the cable connections you have in the setup together with USB.

In my experience, playing back wav files from SD card can also introduce noise from the reading process. It is possible that this is similar when writing to a card.

It could also be relevant what is practical regarding the access to the recorded signal...

I would try out and see what works best for you.
 
To record to the Teensy SD card the output of the audio engine exactly as sent to USB and/or audio adaptor, I made an example in my buffered SD play/record branch.

On the other hand, if you're wanting to send to the PC via USB, then the Teensy appears as an audio device and you can use Audacity or similar to record the data; there should be no noise added, but occasionally there's a one sample glitch if the Teensy and PC get out of step.

If you want to record the analogue signal from the audio adaptor, you need an analogue audio port on the PC, and as @TomChiron says, there will definitely be some level of noise added, and you won't get a sample-accurate copy.

Any analogue signal can indeed be affected by SD card access, especially if you use the one on the audio adaptor - the one built in to the Teensy 4.1 is both faster and adds less noise because the audio pathway shares less of the power; SD cards can take relatively big gulps of current, which puts noise on the power rails.
 
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