Choose first DSP - processing guitar signal

Hi,

I'd like to get started using DSPs. And as I'm a guitarplayer I thought a guitar effect would be a great point to start.

I won't start with an expensive DSP like the TigerSharc (Fractal Audio's Axe FX II) or an ADSP-21469 (Line6 Helix or Fractal's AX8) - tough I like the specs of both of them .
But I want to play around with

  • EQing
  • modulation filters
  • compression
  • reverb
  • delay
  • bandfilters
  • maybe later even a looper (using some external memory)

I need the DSP to be at least 24bit 96kHz.

I've read an ADAU1701 would be a nice and cheap device to get startet. But it lacks of memory, why it's not usable for a reverb. An ADAU1452 shall have enough memory for an reverb but lacks of ADC and DAC. Then some guys told me the ADAU1452 wouldn't be a generalpurpose DSP.

So I wonder which DSP to choose.

For delay/looper I'd like to add external ram later on, when I know what I do. But I'd like my first board to be able the rest of the effects.
Also I'd like it to be a newer device which is not EOL, soon.

  • I forgot to mention I'd like to stay within 100-200€ for my first Eval-Board + Software (if software isn't free/opensource it should fit the bill!).

  • 0
    •  Analog Employees 
    on Jun 19, 2018 7:51 PM

    Hello newmike,

    The ADAU1701 is a perfect platform to start with. You have a lot of things to learn about so starting with a simpler device is best to make the pain a little less. The converters built in simplifies the design. Yes, you cannot do a great reverb but you can do something. Check out 's posts and this one shows how to do a reverb with the 1701. https://ez.analog.com/thread/95200-guitar-reverb-and-adau-1701

    You can get familiar with the programming tool and how to use it. The 1701 is a great platform for this.

    Then after you can graduate to the 1452 family.

    Whoever told you that the ADAU1452 would not be a general purpose DSP is correct. It is not a general purpose DSP, it is designed for audio use and that last time I checked a guitar is still an audio device. (I guess unless it is a MIDI guitar! ). Since it is designed for audio use it is well suited for use to process audio, it does it fast and the GUI programming tool makes it easy. The Software is free and the USBi programmer comes with any of our evaluation boards.

    If you go with a general purpose DSP then the costs of development will be much higher and the complexity is far greater. The SigmaDSP line has been so good for simplifying audio specific DSP applications.

    Also learn how to use this forum and how to search older posts. There is a lot on the forum to help you.

    Enjoy!

    Dave T

  • 0
    •  Super User 
    on Jun 19, 2018 8:50 PM

       David, thanks for mentioning me!  I agree that the -1701 is the best place to start, even though it can't do everything on Mike's list.  Many of us have cut our SigmaDSP teeth with this one.  With built-in converters, self-boot and GPIOs, it's self-contained and easy to work with.  And we can do amazing things with it.  Getting as much as will fit from its capabilities is half the fun.

       Mike, we know that everyone in the business brags about their bit depth and sample rate.  You'll find the ADAU1701 somewhat limited when running a 96K sample rate -- where it can perform only about 500 instructions per sample, half of what it does at 48K.  The good news is that the Sigma-Delta converters and other design features of the -1701 make the most of 48K -- the chip sounds quite good there.  And with the average guitar speaker topping off at 5 KHz, a 96K rate yields diminishing returns.  In short, you'll have a lot more fun working with the -1701 at 48K.

       Best regards,

       Bob

  • Hey Dave, thanks for your reply.
    Why would you start with the 1701 and after that use the 1452? Wouldn't it be better to start with the 1452 from the beginning? Especially as it's capable to use the reverb...without workaround.

    In general I'd prefer to use one platform that might fit for all my needs - even ram extensions.
    Working on this project might take month or even years before I'm at the point I'd like to be.
    Changing platform within this process will need more time to get the new devices work.

    What about the Blackfin series? I've seen there are some boards below 200 bucks. But they are intended to be used with the CrossCore Embedded Studio - but I couldn't find pricing information. Is there a free (or cheap educational) version to be used with the dev-boards?
    On a blackfin-list it looks like nearly every blackfin is able to access external ram.

    If I start using an 1701 and would like to switch over to the blackfin series later, would I benefit or my SigmaDSP-knowledge or would I start from the beginning? (besides basic DSP knowledge - that's what I'm going to get reading some books and talking to some devs at work).

    Bob, thanks for your reply. I'll have another look on the 1701, but I'm doubtful if it's the right device.

  • 0
    •  Analog Employees 
    on Jun 20, 2018 2:07 AM

    Hello newmike,

    You asked for my opinion so I gave it. I think you should start simple and work up. You are correct, there will be another learning curve if you go with the Blackfin or a SHARK. We do have  SigmaStudio for SHARC but I don't think we have it for the Blackfin. ( I should know that but then I don't work with that part).

    You will find that these other parts can do some really great things but you will have to invest in CrossCore and in third party libraries if you want to do anything fancy. It will probably come to many thousands of dollars and yes, look into educational discounts. If you are planning on becoming a DSP engineer then pick up and learn about as much of these different devices as you can. They all have things they do well and other things they do not do well.

    Another opinion of mine is that engineers tend to want to pick the Ferrari to go drive down the city street to go get lunch at a local fast food place rather than just taking the VW Bug. The VW Bug will do that job just as well as the Ferrari but at MUCH less cost and complexity! By the way, I have done that once,... taken a Ferrari to go to McDonalds. It was not my car, the client said, "take my car" so I could not refuse!

    So you will find that in more complicated systems it may call for multiple DSPs and the SigmaDSP is great for taking the load off of the SHARC by doing some of the routing and simple processing tasks so knowing what they are good for is not a bad thing to learn.

    By the way, Bob is right, using 96kHz fs for a guitar is simply burning power and MIPS for no reason.

    By the way, if you are also learning about PCB layout design and will build your own PCBs. Using a Blackfin with external memory is like trying to learn to swim by jumping into the deep end of the pool. I say start simple and work your way up. You will learn important concepts along the way.

    Dave T