@whollender: no, there was no noticable noise of that extent.
A FFT analysis revealed lots of humming from low-frequency AC, but as far as I can tell, that is actual sound from electronic devices.
Being able to record beyond chunk sizes the RAM can hold has many advantages for "primitive" audio quality testing, as one can capture normal voice and music, vary in loudness and move the microphone around to verify that it is picking up real sound sources instead of internal distortions.
Your board looks really good, do you have more information available?
Looking at the pictures, U202 and U203 isolate the digital ground on the teensy (connected to a computer, which may bring all kinds of noise) from your main ground on the board. It follows that U301 is the 28-Pin TSSOP CS4272 chip which controls the show, and to the right are your stereo input and stereo output stages.
The 4 individual groups suggest that you have differential audio connection towards the outside world (probably to keep the audio quality high) .. but what I yet don't understand is the fact that you need four 8-Pin SOIC chips (2x input, 2x output) for that.
I thought a single LME49721 was already designed for dual channel (=stereo) operation - do you need this configuration for the differential output?
A FFT analysis revealed lots of humming from low-frequency AC, but as far as I can tell, that is actual sound from electronic devices.
Being able to record beyond chunk sizes the RAM can hold has many advantages for "primitive" audio quality testing, as one can capture normal voice and music, vary in loudness and move the microphone around to verify that it is picking up real sound sources instead of internal distortions.
Your board looks really good, do you have more information available?
Looking at the pictures, U202 and U203 isolate the digital ground on the teensy (connected to a computer, which may bring all kinds of noise) from your main ground on the board. It follows that U301 is the 28-Pin TSSOP CS4272 chip which controls the show, and to the right are your stereo input and stereo output stages.
The 4 individual groups suggest that you have differential audio connection towards the outside world (probably to keep the audio quality high) .. but what I yet don't understand is the fact that you need four 8-Pin SOIC chips (2x input, 2x output) for that.
I thought a single LME49721 was already designed for dual channel (=stereo) operation - do you need this configuration for the differential output?