jardenblack26
New member
Does anyone know if the Teensy 3.x boards have an analog anti-alias filter as part of the 2 built in ADC's and what it's bandwidth would be?
Thanks much!
Jarden
Thanks much!
Jarden
AFAIK, the SGTL has a FIR filter with fixed coefficients as an anti-aliasing filter. It is clocked with the word clock, thus, it adapts to the sampling rate automatically.
However, I am still not convinced the SGTL5000 has a built-in anti-alias filter. The reason is that in three of my projects I use the SGTL5000 audio board with sample rates higher than 44.1ksps and all frequencies come through.
But did you witness any aliasing if you applying an input signal that's above half the final sample rate?
If it is indeed sigma delta followed by CIC digital filter, then no steep AAF is needed, only the typical single pole LP filter at the input of the ADC.Paul, thanks for your test results, they are pretty convincing for 44.1ksps sample rate.
To be honest, I did not check or test that systematically for higher sample rates. You are probably right that one would have to check that systematically by injecting frequencies above half the sample rate and look at the output of the codec.
I am not familiar with CIC filtering: is it possible that a CIC anti-alias filter in the codec also scales with sample rate?
All the best,
Frank
The CIC filter is a special case of a FIR filter, thus no contradiction. And if it’s clocked with something proportional to the word clock, it would automatically adapt to the sample rate and thus to the input bandwidth