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Topic: arduino synth and sequencer (Read 339 times) previous topic - next topic

radop

Hi all, I'm new here :)

Could somebody, please, check my schemes? I'm quite noob in electronic circuits, so it would help me.

It's suposed to be synth + sequencer outputing on DUE's DAC. For now it's just prototype, but I would like to make foot controlled polyphonic synth with sequencer for guitarists, etc. Those pots are meant to be pedals, they will modify synth's parameter (for example oscilator's frequency or envelope's parameters) and will have up, down button each for parameter change and LCD dsiplay which will show parameter's value. 7-segment should display number of current/active sound/track (changable using up, down buttons). Active sound's sequencer would be editable by those 8 buttons.

I made the circuit based on circuits I found:
  • http://www.instructables.com/id/Turn-your-Arduino-into-a-4-voice-wavetable-synth-w/?ALLSTEPS
  • http://rcarduino.blogspot.sk/2012/08/the-must-build-arduino-project-illutron.html
  • https://learn.sparkfun.com/tutorials/build-an-auduino-step-sequencer
  • http://www.arduino.cc/en/Tutorial/HelloWorld


What I really am not sure is the line output - what I mostly found was made for UNO or used amplifier (which I don't want to use - I just want to have line out and use external amp and speakers). Is it ok like that? Is it even line out what I made? Is the low pass filter really needed when using built in DAC? I found (http://electronics.stackexchange.com/questions/101274/audio-from-arduino-dues-analog-outputs-to-line-in) that the coupling capacitor is there just to be sure (most amps/line ins should have such capacitor). What about the op-amp method mentioned in stackexchange - is it good enough without it?

But I will appreciate overall advice :)

Thanks.

radop

Hi, any advice? :)

I had some electronics course this semester, so now I know the low pass filter at the output should cut out everything above 657 Hz (if I did the math right) - isn't it quite low?

Any help appreciated.

Rado.

Palliser

Hi, any advice? :)

I had some electronics course this semester, so now I know the low pass filter at the output should cut out everything above 657 Hz (if I did the math right) - isn't it quite low?

Any help appreciated.

Rado.
Hello radop,

I just did take a look at your schematics and here my thoughts,

I am sure that you probably did read the notes of the Arduino SimpleAudioPlayer example.

Anyway here some tips regarding the implementation of any application using the DAC pins in Arduino Due.

1-NEVER connect the DAC pins directly to the speaker. If you do so, you shall burn them.
2-Use an amplification circuit between the DAC pins and the speaker.
3-The LM386 based amplifier recommended by Arduino is very simple and should make it for you. Anyway,  I'd recommend you to consider using the SPI or I2C serials of Due connected to an Audio Codec device (i.e. Wolfson WM8731  ~US$19) as an alternative.

Here the Arduino SimpleAudioPlayer link, just in case.

https://www.arduino.cc/en/Tutorial/SimpleAudioPlayer

Regards,

-p

Paul Stoffregen

#3
Jun 21, 2016, 03:33 am Last Edit: Jun 21, 2016, 03:35 am by Paul Stoffregen
But I will appreciate overall advice :)
Over the last couple years I've been developing an audio library for Teensy 3.2.  It's similar in capability to Due, but uses a completely different chip, so the code isn't directly compatible.  The Teensy has a Cortex-M4 and this library uses the M4's DSP extensions for the audio processing (Due has Cortex-M3 which lacks the DSP instructions).  There's also a shield with a codec chip, which is needed for good quality sound output.

Last year we made a workshop and huge tutorial video showing the major features.

https://www.youtube.com/watch?v=wqt55OAabVs

The section about oscillators and envelops starting at 25:04 might be interesting for your synthesis needs.  The library is capable of running many of these oscillators and envelops and other effects simultaneously.

But unlike Arduino Due, a limited number of pins are available.  You might need to add extra hardware like a 2nd board and communicate between them with serial.  In fact, if you go this route, you might use the Due with its many analog pins for connecting all those pots and have it send data by serial to the Teensy which could perform the synthesis work.

Even if you don't use this, hopefully the video is at least interesting?

radop

Hi, thanks for reply.

1-NEVER connect the DAC pins directly to the speaker. If you do so, you shall burn them.
2-Use an amplification circuit between the DAC pins and the speaker.
3-The LM386 based amplifier recommended by Arduino is very simple and should make it for you. Anyway,  I'd recommend you to consider using the SPI or I2C serials of Due connected to an Audio Codec device (i.e. Wolfson WM8731  ~US$19) as an alternative.
Yes, I'm aware of not connecting dac directly, but is it not enough to use low pass filter + dc coupling capacitor at the dac output?



Over the last couple years I've been developing an audio library for Teensy 3.2.  It's similar in capability to Due, but uses a completely different chip, so the code isn't directly compatible.  The Teensy has a Cortex-M4 and this library uses the M4's DSP extensions for the audio processing (Due has Cortex-M3 which lacks the DSP instructions).  There's also a shield with a codec chip, which is needed for good quality sound output.

Last year we made a workshop and huge tutorial video showing the major features.

https://www.youtube.com/watch?v=wqt55OAabVs

The section about oscillators and envelops starting at 25:04 might be interesting for your synthesis needs.  The library is capable of running many of these oscillators and envelops and other effects simultaneously.

But unlike Arduino Due, a limited number of pins are available.  You might need to add extra hardware like a 2nd board and communicate between them with serial.  In fact, if you go this route, you might use the Due with its many analog pins for connecting all those pots and have it send data by serial to the Teensy which could perform the synthesis work.

Even if you don't use this, hopefully the video is at least interesting?
Thanks for the tip to use teensy with due and the tutorial - I'll take a look at it.

Rado.

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