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Thread: Programmable fx pedal looper

  1. #1
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    Programmable fx pedal looper

    I have also posted this in the project guidance forum.
    Hello Hive mind of the Teensy audio world.
    The question/questions I have are a culmination of the information acquired and direction I was sent in by one of the Arduino forum user that a Teensy board would be the route to go for what I wanted to build.

    I am trying to walk that newbie line of being able to give the intel required to get the help you are able to give and sort of cover the degree of skill I might not have in explaining myself. These are the main links I was using as inspiration.

    https://youtu.be/NYT-uuoJm2o.
    https://www.instructables.com/id/Ard...edal-switcher/

    The build idea is to make a rehoused Boss LS2/Arduino now Teensy hybrid switcher: *Keep the simplicity of the 3 dial control, (loop A volume, loop B volume and dial for selecting the pedals set up) the boss LS2 affords me.
    *I want to use 4-5 Boss LS2'S to be able to alter the sound, especially for live work. With 3/4 spare toggle switches for multi combination use of the preset sounds already being used via the LS2s.
    *Combined with the Arduino's/Teensy's ability to make 1 touch switching easier, (for live music work). I found out that I couldn't just drop the Boss LS2'S directly into the Arduion switching chain, (replace the boss pedal switch for the Arduino's toggle switch). This was due it having a bistable circuit. Which meant it had to have extra circuitry or that section had to get bypassed for my grand idea to work.
    So now rather than telling it to be on and off. I have gone the conventional of having the pedal permanently turned on and just selecting if the the audio signal got put in or out of the signal path as is normal when making an Arduino based switcher.
    *Also I will need my clean sound, (original signal entering the switcher from instrument) running through the switcher when no toggle switches are engaged and if the switcher looses power for any reason. I would like the signal path to be what they term as tru bypass. So when trying to complete the song or the set it will able to be done.
    I will be trigger off the toggle switches with my feet as my hands will be busy hitting and plucking strings.
    For the project I would have been using the Arduino at ATMEGA board for a certain level of future proofing incase I wanted to add more loops or have it control multiple other devices. Not being familiar with Teensy I don't know what the best board will be for my needs and if I other boards to make it all work together. I haven't been able to find a build guide or coding guide in the same way I have with the Arduino. Any help, direction or hand holding much appreciated.
    Thank you for your time.

  2. #2
    It's going to be very difficult to formulate a reply to this thread because you're not asking a specific question. We can't really answer what Teensy would be "best" because we don't know what that might mean.

    I might make a couple observations that I hope are helpful though:
    1 - the Teensy audio library is best suited for working with digital audio signals, and it's not clear to me if this switchable looper thing needs to digitize the audio at all. In the video, it looked like mostly passive components, so perhaps a Teensy is overkill?
    2 - have you already built a DIY version using an arduino of some kind? If so, that might enable you to ask a more specific question like "how do I implement this specific feature?" or "how much RAM is needed to do such-and-such?"

    I don't want to come off as rude, it's just I have no idea how to help.

  3. #3
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    Hi wcalvert,
    Even with my limited knowledge. I to believed no audio signal gets digitized at all. As all I am wanting to do is a just control what the swiches are doing amd multiple triggering of switches.
    As the in's, out's, loops A&B are all being controlled off the LS2 and I am just fundimentally thinking of putting the switch in front of the LS2 to control its in and out status in the signal path.
    I am affraid I haven't even made an Arduion DIY project let alone ever made an Arduino project of this one.
    So have no idea how much RAM would or could be required. I just want a smooth running system and have always understood more RAM the better. I was in the process of trying to find out as much info about this looper pedal when someone recommend a Teensy board for its size, no need for the relays and thought it a better fit for my project.
    I would like my purchase of a teensy board, if it is the right thing to do. To be slightly future proofed by being able to access more in's and outs than I currently need and the ability to midi control any other purchases I might make. Hope this gets us abit closer to being able help me.

  4. #4
    Ah, okay, I think I'm starting to understand a little more.

    Well, yeah more RAM is generally considered good, but keep in mind, teensies and arduinos do not have an operating system to battle with. Even a lowly Arduino Uno with 2kB of RAM will respond on a timescale that seems instantaneous to us humans.

    Would it be possible to start with one of the existing DIY designs, build it start to finish, and then add or tweak the design to do what you're wanting? Considering that you're new, I would definitely recommend starting with something that is known to work. The learning curve will be significant, and a working project will teach you quite a lot.

  5. #5
    Senior Member oddson's Avatar
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    There are integrated circuits for this.


    Mono A/B with something like this

    https://www.analog.com/en/products/adv3219.html

    Something like this could do A/B stereo

    https://www.analog.com/en/products/ad8182.html

    Something like this can do 16 inputs x 16 outputs?

    https://www.analog.com/en/products/ad8113.html

    You don't need the audio library at all and any Teensy can handle the minimal computations required.

  6. #6
    Senior Member oddson's Avatar
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    Your design goals are a bit hard to decipher. How many inputs and outputs and do you need to send outputs back to inputs?

    If you can draw the analog signal path that might help.

  7. #7
    Senior Member oddson's Avatar
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    I gather the appeal of "True Bypass" is why you are looking at relays?

    If you feel that need I'd recommend a prebuilt relay modual that handles the switching electronics for you which makes it very much like using an IC switch in that you need only signal voltages to control pins. Needs to be double pole for true bypass wiring.

  8. #8
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    Quote Originally Posted by KidDing View Post
    Hi wcalvert,
    Even with my limited knowledge. I to believed no audio signal gets digitized at all. As all I am wanting to do is a just control what the swiches are doing amd multiple triggering of switches.
    As the in's, out's, loops A&B are all being controlled off the LS2 and I am just fundimentally thinking of putting the switch in front of the LS2 to control its in and out status in the signal path.
    I am affraid I haven't even made an Arduion DIY project let alone ever made an Arduino project of this one.
    So have no idea how much RAM would or could be required. I just want a smooth running system and have always understood more RAM the better. I was in the process of trying to find out as much info about this looper pedal when someone recommend a Teensy board for its size, no need for the relays and thought it a better fit for my project.
    I would like my purchase of a teensy board, if it is the right thing to do. To be slightly future proofed by being able to access more in's and outs than I currently need and the ability to midi control any other purchases I might make. Hope this gets us abit closer to being able help me.
    Why would you want to use a switcher to control a bunch of other switchers? If your plan is (like in the video) to build a loop switcher for selecting different combinations of FX pedals then you don't also need the LS2 pedals. The switcher has, say 8 send and return jacks which you connect your pedals to and you leave all pedals ON. The patch select footswitches then turn on or off the relays that either send the audio out of the send jack on the switcher to the input of a pedal and takes the signal back from the pedal output into the return jack, OR, the relay bypasses that pedal completely.

    The program running on the microcontroller accepts inputs from the footswitches and controls the relays. I'm not sure if the YouTube project really needs an Arduino Mega. For four footswitches (one Bank select and three patch select) plus 8 relays (or 16 if they are not DPDT?) there should be enough in/out pins on a Uno or Nano to do the job - and they'd be much smaller!

  9. #9
    Glad you posted that GuitarPhil. I was mystified how totally passive components could do any form of looping (like, sample looping)... now I see "looping" in this case means just signal routing.

  10. #10
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    GuitarPhil you are right on track.
    Oddson thank you for confirming what I thought concerning relays being the preferable route to do ro get tru bypass. Wcalvert sorry for the mix up in language I was always slightly worried if all the terms I understood translated over to the people who understand the how behind the why it works the way it works. I am just taking baby steps at the mo.
    Now that I feel we are probably able to talk shop, I hope. I shall try smarter to explain.
    The thing about using the switcher to toggle through switchers is. I not a fan of any of the multi ones on the market because they don't do what I want them to do with simple amount of control I want to use to do it. Low end ones don't have the control I require and the top end ones are to expensive and its all sub menu's of a menu. The LS2 has a volume for each loop and a preset for what you are telling the loops to do and essential asigning what pedal will doing when you engage it. All I have ever wanted to do is be able to turn on and off or take in and out of the signal chain single or multiple LS2ís at anyone time and not tap dance to shut off one set of sounds to be able to gain another set of sounds. When it might able to be done in one tap of my foot. Complicated sounding I know but when you are in the heat of battle on stage. You don't want to toggling through a tonne of menu's just to be able to adjust a parameter.
    So I hadn't even found what I was looking for, really. I was just looking at the best one I could modify for my use.
    I have worked out with help that due to the bistable circuit in the LS2 that just replacing the switches with momentary DPDT or SPST and hooking up relays wasn't going to work simply because how they choose to do that part of the boss pedals circuit. I will get round this by hooking up all the LS2'S switches to one switch and when they are powered up pressing the button and hopefully turning all of them on. The trial of turning on two powered boss pedals together with a random lawn mower momentary switch worked. So I thought I could do all my LS2'S that way.
    Then it was onto just putting the audio in and out of the signal chain. I thought I accomplish this via having the correct switch in place between the in and out sockets of the LS2. And then running it to a relay of some kind because I want "tru bypass" to cover any problems and also to cover any individual pedal problens if the power goes or it should down in anyway.
    Then the next question was what circuit to use, to do all the actual programming of all the switching I might want to do. With an eye to future about wanting to add more switching parameters and maybe midi control, future proofing to some degree was at the back if my mind.
    I want 8 switches.
    Ideally I will use 5 LS2'S circuits (5 switches).
    Then I have 3 swiches left over for being able to program them to set off more than one of the other switches at once. Which equates to multiple sounds in my world.
    I have really just been trying to find out how to do this, keep the costs down as s much as is sensible and use the right parts to do it. Thank you again for you patience with me.

  11. #11
    Senior Member oddson's Avatar
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    Relays may allow one to claim 'true bypass' but contacts can be noisy and if you use IC switching you are 'bypassing' the loops if you switch both the output and input of the loop with double pole wiring (although you would likely buffer the signal anyway making much of the whole issue moot).

    But guitarists tend to like marketing more than electronics so 'tru bypass' tends to mean metal contacts and infinite impedance.

    So how many loops and do you need to switch the order in which they chain?

    If you can produce a wiring diagram that would allow the switching (level control?) you are after then the microcontroller code can do the tap-dancing for you... but you need to work out the signal chain if you have not already.

    Then the difficult bit is figuring out how to tell the controller what to do when any given button is pushed. It's easy enough to hard-code behaviour to a button if that's all you want but making it flexible is what leads to menu-driven complexity.
    Last edited by oddson; 09-13-2019 at 04:27 PM.

  12. #12
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    Oddson there will only be 3 loops that will really need or want the ability to change the signal chain order. As the 5 orignal switchers will be fixed in the correct signal chain order and I don't need pedal 5 to become pedal 1 and 2 swaps with 3. I hope the case will be that I can use any of the switchs to turn the sounds on and off with one touch. Putting any pedals effect in to the path and then if there is no effect needed next putting that same pedal sound out and back to the original clean sound running through. In the same way if I want to jump from one effect to another I want to do it in one hit. Turning one off as I turn another one on whether that is engaging one sound or multiple sounds.

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