Line level of teensy audio output?

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jayfehr

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The Teensy 3.6 board lists "I2S Audio Port, 4 Channel Digital Audio Input & Output" as one of the features. Does anyone know what level the audio out is?

I would like to use this for a guitar pedal, so if it's at instrument level (-20dbu, as opposed to consumer line level -10dbu) then I'm a happy camper and can just run audio into and out of the board.
 
jayfehr said:
The Teensy 3.6 board lists "I2S Audio Port, 4 Channel Digital Audio Input & Output" as one of the features. Does anyone know what level the audio out is?
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I2S is digital data. The analog levels depend on the ADC and DAC chip which converts to analog signals.

If you use the audio shield with SGTL5000 chip, the levels are configurable. See this documentation (right side, scroll down to "Signal Levels"):

http://www.pjrc.com/teensy/gui/?info=AudioControlSGTL5000

Of course, if you need different levels, it always possible to add opamps....
 
Ok, I got it. I thought those were separate audio features. An I2S port and a 4 channel I/O. Sorry my bad.

I was just hoping that I could skip the audio board, but I'll order one.
 
You can also get audio input from an ADC pin and output on a DAC pin. Currently only 1 of each is supported, but the code will soon be added for 2 DAC and 2 ADC.

The sound quality isn't as good as the audio shield, especially the ADC has no anti-aliasing filter to remove frequencies above 22 kHz, but it still might be ok?
 
Thanks for the info. I'll start there (since I already have the Teensy, but not the audio board). My ultimate goal is to make a guitar loop pedal (similar to the BOSS RC-3). The recording aspect seems pretty straight forward with the audio library (awesome work by the way), so I'm trying to find the best way to get instrument level inputs into, and out of the teensy. These levels would also be necessary for any other guitar pedal projects.

I've found lots of numbers, but they don't all work together. Whenever I look up what line level or instrument level is, I get +4dbu (pro line level), -10dbu (consumer line level) or -20dbu (instrument line level). But when I look at any dac's or codecs they are all in voltages. A few people make it clear to be careful about the current, but I have no idea what the appropriate amperage should be. It's been a fun research project, and I've learned lots, but I'm not any closer to building the thing yet. I may just use my multimeter to measure the voltage and current from the cable as I play and see the range of readings I get there and go with that.

One thing I do know, is once I have all this figured out I will be writing it up and posting it somewhere for others.
 
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