Introduction: DIY Chewie Monsta Looper (Based on Ed Sheeran's)
I will admit that I had heard of Ed Sheeran for a few years now and never really paid him much attention. I liked some of this songs on the radio but thought he was just another pop artist until I say him perform "Shape of You" at the 2017 Grammys. I was blown away! I didn't really even like the song but to watch him perform it live by himself with his loop pedal was mesmerizing. I scoured the internet looking for info on this pedal and found that there wasn't much out there. I final found some articles saying that it was custom built by Ed and his guitar tech which disappointed me until I finally came across and Instructable by "edsutcliffe" ( https://www.instructables.com/id/DIY-Chewie-Monst... ) that had the "secret sauce" on exactly how it worked. I was pumped because now being an engineer I new I could build one of these so I got to work. However, while working through the instructable I ran into several "gotchas" along the way which is why I wrote this instrcutable. edsutcliffe's page does a great job of describing the pieces and how they go together. My intention here is to fill in some of the gaps that drove me crazy and cost me hours if not days of time trying to solve problems. So while Im not going to walk you through step by step how to build the loop pedal (most of which you can find on edsutcliffe's page), Im going to walk you through the key integration issues that plagued me.
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Step 1: The Pedal
While seeming to be the most critical piece, the pedal itself is the easiest and most straight forward part of the project. My advice here is to start slow and build a rough mock up first and experiment with it. I found that until you actually start using it that its difficult to know what you want. You may think that three tracks are enough but after playing a bit you may find that you really would like a fourth track. Changing it later isn't the easiest thing to do. Even while I was building my second version of the pedal I went back and forth about adding a button for "UNDO" but decided against it. I later found that it we really be useful but I didn't leave enough space for it. I ended up having to take the "programmers" way out and multitask the CLEAR button. Now I have it so that a short press triggers UNDO and a long press triggers CLEAR.
Beyond that, the only other consideration here is whether you want to use pedals or foot switches. I went with foot switches initially just for cost but I recently built a second board using pedals and found them much easier to use.
There are lots of options on Amazon but the ones I used are below.
- Foot switch (10 for ~$20) https://www.amazon.com/Etopars-Guitar-Effects-Mome...
- Nail covers https://www.amazon.com/gp/product/B07922M54B/ref=o...
- Pedal (~$10 per) https://www.amazon.com/gp/product/B00DGXZBJI/ref=o...
Step 2: Arduino
In the instructable, rather than telling you to just by a manufactured Arduino board it list each component and has you build your own. In my opinion this is ridiculous given that a mfg board cost ~$10 on the internet so do yourself a favor and just go with that.
Now down to my first "gotcha". One important item that isn't discussed anywhere is how to create the sketch (code) for the Arduino which is pretty critical since the buttons wont do anything without this. So Im providing my code for you to use. Again, Im not going to walk you through step by step how to program the Arduino. If you go to their homepage they have plenty of tutorials on how to do that. If you are savvy enough then feel free to edit it however works best for you.
- The pedal has 8 buttons and 2 LEDs
- A button press sends a MIDI command message from the Arduino
- Buttons (While I'm describing each button's function, the Arduino code itself does nothing but send a MIDI command. the MIDI command must be tied to a script in Mobius which will be covered later)
- Buttons consist of two groups
- Global = Sends the same MIDI command regardless the mode
- Mode-based = Sends different MIDI command based on the mode
- MODE = this button changes the "mode" of the pedal (Record / Play / Volume Control)
Short press toggles between Record and Play mode
Long press (more than 1 sec) goes to Volume control mode.
- In REC mode = In RESET mode it will start the loop and close the loop on next press and go to Overdub mode. After that it toggles between Play and Overdub of the current track.
- In PLAY mode = Unmutes and restarts all tracks
- In REC mode = Applies "instant multiply" function to the current track.
- In PLAY mode = Mute and Pause all tracks
- In REC mode = In RESET mode it will start the loop and close the loop on next press and go to Play mode. After that it toggles between Play and Overdub of the selected track.
- In PLAY mode = Toggle between Mute and Play
- In Volume Control mode = Track 2 cycles through the tracks, Track 1 reduces the output level (volume) of the current track by 5, Track 3 increases the output level of the current track by 5.
- RESET = applies "Global Reset" function
- Short press (<1000ms) applies "UNDO" function to the current track
- Long press (>=1000ms) applies "CLEAR" function to the current track
- REC LED = Red, on when in Record mode.
- VOL LED = Blue, on when in Volume Control mode.
- REC/PLAY = pin 3
- RESET = pin 4
- X/STOP = pin 5
- CLEAR = pin 6
- TRACK 1 = pin 7
- TRACK 2 = pin 8
- TRACK 3 = pin 9
- MODE = pin 10
- REC LED = pin 11
- VOL LED = pin 12
Note: A community friend, Claudio, made some enhancement to the sketch and shared it back with us. Thanks, Claudio!
Step 3: The MIDI Interface
This is an area I feel wasn't cover very clearly in the other instructable. Basically, as discussed in the Arduino section, the pedal and Arduino just outputs a MIDI command based on the button pressed. In order to be used you need to send the MIDI to the PC running Mobius. I found 3 ways to do this and it's dependent on the type of audio interface you buy (more to come).
- Option 1 - Depending on what audio interface you buy, some have built in MIDI in/out ports. If this is the case then you can just follow the instructable and pull out the serial channel on the Arduino and connect it to the MIDI In port. You will then be able to select this as your MIDI controller source later when you setup Mobius
- Option 2 - My audio interface didn't have a built in MIDI port so this presented a challenge. So I initially pulled out the serial channel as in option 1 and purchased a separate MIDI-to-USB adapter. While this did work, I found it to be clunky and unreliable. Plus I was frustrated because this would be a 3rd USB connection and my PC only had two. I could disconnect the cable to the Arduino which I was using for power and debugging but that meant I would need an external power supply for it.
- Option 3 - I didn't understand why I couldn't get the MIDI commands over the USB connection and have the same connection power the Arduino. I knew there must be a way. After a lot of internet searching I finally found a way by using two freeware apps.
- loopMIDI - Ironically named, this free apps enables you to create a "virtual" MIDI port on your PC. All you have to do is install it and define a virtual MIDI Out port and that's it. It will run automatically at boot up. https://www.tobias-erichsen.de/software/loopmidi.h...
Hairless MIDI - This program enables you to create a "serial bridge" so that you can map the serial COM port used to program your Arduino to the virtual MIDI port you just created with loopMIDI. And Whalla! You now only need a single USB connection from the PC to the Arduino. http://projectgus.github.io/hairless-midiserial/
NOTE: If you choose to use option 3 then you need to make sure that the Arduino code has the serial channel baud rate set to 38400 instead of the standard 31250 that MIDI uses.
// Set MIDI baud rate:
// Set baud rate to 38400 for Hairless MIDI
Step 4: The Audio Interface
I will say now that this is probably the most important component that you will have to select. Since low cost was a key driver for me I looked for an inexpensive audio interface. I ended up settling on the BEHRINGER U-PHORIA UM2 (https://www.amazon.com/Behringer-UM2-BEHRINGER-U-P... ) which you can get from Amazon for ~$30 because it was low cost and had 2 input channels and 2 output channels which is all I needed. There are lots of options out there but it could slightly change the Mobius setup later.
Understand here that you do get what you pay for. While the UM2 does a great job for its price, I occasionally run into issues such as a random "pop" sound if I overdub too many layers or sometime get static and have to reboot the interface. So if you are serious about performing with this pedal then spring for a higher quality audio interface.
I really thought this would be the easiest part of the project but this ended up being the hardest problem for me to solve and almost resulted in me abandoning the project. When you first plug it in to your PC, Windows will automatically install a driver and you think you are set, right? Wrong. After I first set it up and starting recording tracks I found that the latency was so bad (more than a second) that the pedal was basically unusable. I had to be doing something wrong. Again, after a ton of internet searching I found the problem. Windows will install a default MME driver for the audio interface. When you read about these it says that they are very high latency and not suitable for real-time recording. What I had to do was go to the Behringer website and find the ASIO drive for my specific interface. ASIO drivers are specifically designs to minimize latency which is what you need here. After installing this driver the recording latency was not even detectable by the human ear. So the takeaway here is that whatever audio interface you use please make sure you get the ASIO driver from the manufacturer and save yourself the headache that I experienced.
Step 5: Mobius
Let's face it, without Mobius all we have so far is a MIDI controller pedal board. Mobius is a free software program created by Circular Labs (http://www.circularlabs.com/ ) that does all of the recording and looping. It's really an amazing program. That being said, the documentation from Circular Lab I found to be very lacking. After the install you get a window with 8 tracks and tons of buttons, meters, and counter. It took me a while to figure out how to navigate the GUI and configure it for me needs. Fortunately I found a youtube video posted by edsutcliffe that walks you through the configuration step by step.
After that, the only part of the setup that I had trouble with was mapping a certain input channel to a certain track. In the video, they are using a 4 channel interface and each channel shows up independently in Mobius. The UM2 interface that I used actually uses a single stereo channel and utilizes the right and left channels independently. So I only see 1 "channel" in mobius but I can map a single channel by moving the "Pan" setting all the way to the left or to the right. So I have track 1 and 2 with pan set all the way to the right so that only channel 2 (instrument) gets recorded. Then for track 3 I left pan in the middle so that I can record either the mic or the guitar on it. If I want to only record the mic then I would pan all the way to the left channel.
Step 6: Mobius Scripts and MIDI Bindings
The final piece of the puzzle is the Mobius scripts and MIDI bindings. Even though I'm very familiar for computer programming, I found the Mobius scripting language to be a little confusing and not well documented. It took me a long time and a lot of tweaking to get them the way a wanted but in the end they work for what I need.
Well that's it. Hopefully these tips will help you out with your build and you will be able to avoid the frustrations that I ran into.