Can Teensy 3.6 replace [Quad-Audio + Teensy 3.2]?

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madzo0omadz

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Hello guys,

I posted before about Teensy 3.2 and Audio shields and I'm pretty much a pro at them now. It is quiet a hassle to connect the Teensy to two Audio shields (needed for 4 analog input, 2 analog output). I was thinking would it be possible to have all the processing done on the Teensy 3.6 instead of the Teensy3.2 and its Audio shields?

Using the Teensy Audio development GUI, here is the list of Audio specific members I use:

// GUItool: begin automatically generated code
AudioInputI2SQuad i2s_quad1; //xy=269,392
AudioFilterBiquad biquad1; //xy=450,309
AudioFilterBiquad biquad2; //xy=467,491
AudioMixer4 mixer1; //xy=718,351
AudioMixer4 mixer2; //xy=720,445
AudioOutputI2SQuad i2s_quad2; //xy=911,405
AudioConnection patchCord1(i2s_quad1, 0, mixer1, 0);
AudioConnection patchCord2(i2s_quad1, 0, biquad1, 0);
AudioConnection patchCord3(i2s_quad1, 1, mixer2, 0);
AudioConnection patchCord4(i2s_quad1, 1, biquad2, 0);
AudioConnection patchCord5(i2s_quad1, 2, mixer1, 1);
AudioConnection patchCord6(i2s_quad1, 3, mixer2, 1);
AudioConnection patchCord7(biquad1, 0, mixer1, 2);
AudioConnection patchCord8(biquad2, 0, mixer2, 2);
AudioConnection patchCord9(mixer1, 0, i2s_quad2, 0);
AudioConnection patchCord10(mixer1, 0, i2s_quad2, 2);
AudioConnection patchCord11(mixer2, 0, i2s_quad2, 1);
AudioConnection patchCord12(mixer2, 0, i2s_quad2, 3);
AudioControlSGTL5000 sgtl5000_1; //xy=251,227
AudioControlSGTL5000 sgtl5000_2; //xy=581,235


The Audio specific functions I use are:

biquad1.setNotch (0,freq2,0.05);
biquad1.setNotch

sgtl5000_1.eqSelect(3);
sgtl5000_1.eqBands(0,-0.4,-0.5,-0.4,-0.2); //115Hz, 330Hz, 990Hz, 3kHz, 8.8kHz

I know that the SGTLs are the codecs specifically found on the Audio cards, but would there be a Teensy 3.6 equivalent equalizer or so to do the same functionality as those above? or even does that function work on the Teensy 3.6 right away without the need of those Audio Shield specific codecs?

Also, can the Teensy 3.6 support 4 analog channels input and 2 analog channels output?
 

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So far (at least as I know) quad I2S hasn't been tested on Teensy 3.6 yet. It might need minor tweaking for different pin numbers.
 
PaulStoffregen said:
So far (at least as I know) quad I2S hasn't been tested on Teensy 3.6 yet. It might need minor tweaking for different pin numbers.
Click to expand...

Thank you for the fast reply Paul. I believe your answer meant that you still didn't test Quad audio on the Teensy 3.6 along with 2 Audio shields correct?

I guess I wasn't clear about the question, I apologize for that. My question is, can I disregard the Audio sheilds all together and have the same code I had made for Teensy 3.2 and the audio shileds run on the Teensy 3.6 WITHOUT the Audio shileds? It doesn't have to be the same exact code but similar functions like:

1) Mixing Audio channels (minimum 6 channels)
2) Applying equalizers to certain Audio channels
3) Playing Audio from an SD card

Would this be possible with only the Teensy 3.6, and disregarding the Audio shields as a whole?
 
It may be possible to do what you ask, but there are some stumbling blocks you need to understand.

Depending on the audio quality that you are looking for the internal D/A's and A/D's may not be good enough. The Audio shield runs at 16 bit resolution and a 44.1 KHz sampling rate, same as a music CD. This is sufficient for music listening, but some would say that it is not "audiophile" quality, and there is work being done to make better quality audio boards (24 bits 96 KHz). The internal A/D's do run at a 16 bit resolution, but due to multiplexing, noise and sampling time VS input impedance issues, realistically deliver a 12 to 13 bit result. The internal D/A is only 12 bits. These will certainly not deliver a sound quality that would be sufficient for some music listening applications, but may be adequate for effects, sound generation, and some music synthesis applications.

To my knowledge the audio library doesn't currently recognize or support the second D/A channel on the T3.6.

The support for the SD card slot on the T3.6 is still being worked on.
 
Except for 6 channels (4 is the limit for the audio shields), all this can be done with Teensy 3.2.

If those equalizer features use a lot of CPU time, the faster speed of Teensy 3.6 might help.

If this is an "audiophile" application requiring 24 bits and/or 96 kHz or higher sample rates, then Teensy probably isn't your best choice. But if you don't have a very specific technical need, I'd highly recommend reading this article, especially the part about intermodulation distortion of ultrasonic frequencies.

http://people.xiph.org/~xiphmont/demo/neil-young.html
 
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