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Which SigmaDSP for a fun project?

Category: Datasheet/Specs

Hello everyone,

I am new to this forum. I'm an electronics engineer and I plan to make a "fun" audio board for my sons.

At this time I haven't listed all the specs this card should meet, but primarily it will do the following:

- Record a few sentences from a microphone in order to apply effects and send them to an HP when a button is pressed
- Retrieve an audio signal from an analog source in order to apply live effects and send them to an HP
- Generate musical notes from buttons in order to apply live effects and send it to a speaker

The effects are as follows:
- Add echo
- Reverberation
- Wah filter
- Distortion
- Vocoder
- Simulation of musical instruments (music notes)
- etc...

Do you have any idea of ​​a DSP I could use on my board please?
Once the hardware is done, is it difficult to make such a program with SigmaStudio?

  • Do you think the ADAU1701JSTZ would be sufficient for such a project?

  •      Hi Matheu,

         The -1701 is generally a good choice to start out with SigmaDSP -- however, many of your applications need more than its capability.  To help answer your question, let's consider some details of your fun project:

    • Do you envision making a self-contained device (that can run independently of a computer running SigmaStudio)?
    • Need it operate on battery power?
    • Do you plan to lay out your own PCB or purchase one of the assembled boards made by SureDSP and others?
    • If you're making your own design, can you include (and program) a microcontroller?
    • How much user interface do you need?  A few control knobs and switches, or more?

         Here's why the above questions matter.  As you may have noticed by examining the selection tables and/or data sheets, unfortunately there's no one chip that has everything. So, choose based upon what's important to you:

         First, note that no SigmaDSP is set up for storing and playing back long audio passages.  The SigmaDSPs have some delay memory for reverb and such, but not enough for record/playback use.  Instead, I'd recommend one of the dedicated record/playback chips that use linear predictive coding or another compression method.

    • The ADAU1701 self-boots from an external EEPROM, which you can load from SigmaStudio.   Thus, you need no microcontroller to boot it.  It can handle up to four control pot inputs and a few digital (switch or button) inputs.  It uses a moderate amount of power (3.3V, 110 mA) -- a bit much for battery operation, but not impossible.  It has built-in ADCs and DACs for analog input-output convenience (but you'll need to add a microphone preamp).  You'll get about 1015 instructions at 48 KHz sample rate -- enough to do some of your fun things, plus a few you haven't thought of yet.
    • The ADAU1761 includes a microphone preamp, built-in converters, is low-power for battery operation, and can run more instructions.  But it doesn't self-boot, so if you wish to run independently of SigmaStudio, you'll need a microcontroller.
    • The ADAU1452's Sigma300 DSP core is far more powerful, thus more likely capable of your more complex ideas.  It can handle up to six control pots, and digital inputs as well.  If self-boots too.  Yet, it lacks built-in converters, so you'll need an external codec (converter) chip as well as a mic preamp.  And it uses the most power of these chips.

         I'm not familiar with the various ready-made SigmaDSP boards out there, yet there are definitely some with the ADAU1701 or the ADAU1452.  They usually include some support chips as well.  Considering your applications, I'd rate those a -1701 can handle as a "1", and those which need more processing power as a "2":

    - Add echo  2
    - Reverberation  2
    - Wah filter   1
    - Distortion   1
    - Vocoder     2
    - Simulation of musical instruments (music notes)   1 - 2

         Some of these are easy to program in SigmaStudio, while others (like the vocoder) will take work (if possible at all).  You'll just need to play with programming, making all the usual beginner's mistakes which is the fun of learning.  Feel free to ask more questions.

         Best regards,



  • Hi Bob,

    Thank you very much for all these complete explanations!

    Here are my answers to your questions:

    I plan to make a self-contained device, which works without any computer. It will operate on battery power and I’ll make my own PCB (I have my boards made and assembled by JLCPCB). I can include a microcontroller on the board (probably a PIC µcontroler). I don’t need much user interfaces. If I need more than provided by the DSP, maybe I can use GPIO on the µcontroler which will communicate with the DSP to take into account additional user interface.

    For the memory I noticed that Sigma DSP memory won’t be sufficient.

    Here is what I plan to make, but I’m not sure it will be possible:

    • Capture and apply effects to a recorded sentence
    • Store the final digitalized sentence into an external memory (type to determinate)
    • When a button is pressed, recall the digitalized sentence to go through the DAC of the DSP
    • Play the sentence in an HP after the amplification of the signal

    When you say ‘one of the dedicated record/playback chips that use linear predictive coding or another compression method’, do you have IC examples to give please?

    According to your ‘1’ and ‘2’ notation, I understand that I can’t make effects like echo or reverb with the ADAU1701 and the ADAU1761.

    • Don’t you think the 40ms delay of the 1701 would be sufficient for these 2 effects?
    • If no, I can’t choose the ADAU1452 because it costs about $18 on JLCPCB and I plan to assemble 5 boards (so, $18x5 = $90 only for this IC). I see that the ADAU1761 only costs $5. It has not enough user interface, but I can use GPIOs of the µcontroller which will communicate with the Sigma DSP by SPI, I2C or serial. In this case, is it possible to do more fun effects like echo and reverb, by lowering the sampling rate of the ADC to 24kHz or even 12kHz?

    At last, I don’t understand how to program the Sigma DSP when the program has been generated in SigmaStudio. Do I need an USB to serial programmer?

  •      Hello Matthieu,

         To answer your last question first, you need an interface board often called a USBi to load and control your SigmaDSP directly from SigmaStudio.  Analog Devices sells them -- there's also USBi clones out there although I haven't used any of them.  When designing your board, include a header for the USBi and jumpers to connect the I2C / SPI from your PIC.  This way, you can run your DSP from SigmaStudio to experiment with its functions, then later run standalone with the PIC.  See AN-1006.

         Google ISD1820 for a voice recorder chip.

         40 mS makes a poor-sounding echo (I've tried it).  However, a "trick circuit" can have a -1701 or a -1761 serve up a rather good reverb -- see this post.   Running a lower sample rate can also make better use of your delay memory, although it won't give you more instructions to use.  This FAQ describes what's involved.

         Best regards,


  • Hello Bob,

    Thank you for these new answers!

    The EVAL-ADUSB2EBZ is expensive! I will check if there is a reliable clone of this card.

    The Google ISD1820 looks interesting but I would prefer an IC rather than a board. I didn't come to find one.

    Finally, I think the ADAU1761 will be perfect for my project. For effects that require more computation, I'll lower the sample rate. Now I have to think about how I will record the audio samples. I don't know if it's best to record in analog format, before ADC conversion or if it's best to record in digital format, after ADC or after applying effects. To be honest, I don't know if it's possible/easy to transfer the digitized samples into a 'classic' memory IC like Flash or RAM for example.

  • Does anyone have an answer to my last question please?

    I would like to know if it is possible/easy to transfer digitized audio samples into a "classic" memory IC like Flash or RAM for example. If so, what type of memory would be best for this kind of operation?