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Zero Budget Pedalboard

Adventures in the quest to make the most noise with the least money

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Twelve years ago I bought one of the cheapest DSP guitar multieffects on the market, the Behringer V-amp 2. Although it has been joined by a younger brother (a V-amp 3), two distant cousins (a Digitech RP155 and RP80) and various other siblings, it has obstinately retained its usefulness. But coordinating such a diverse family of signal torturing devices with the touch of a button is not trivial. This project aims to solve the control issues and somehow fit everything in my clamshell pedalboard, all while strictly using stuff I already have lying around.

Background

I am not a musician. My formal education is in the visual arts and graphic / interface design. But I’ve always found myself around musicians and artists of all kinds, and somehow being a vaguely tech-savvy metalhead kid has turned into a 10-year-long career in mixing live bands, building and fixing audio (chiefly guitar-related) gear. To the extent that live mixing had become my ‘day job’, before COVID-19 took that away.

In that context, through hand-me-downs from my audio engineer dad and musician friends and by accepting gear in lieu of payment, I managed to amass some collection of odd guitars, effects and amps, usually in various states of disrepair. I’ve certainly spent more time working on than playing through them, but that’s what seems to amuse me so occasionally I’ve taken upon myself to organize my effects into something no bedroom guitarist can be without: an overcomplicated pedalboard.

Appropriately lo-fi picture of the first edition of my pedalboard, from 2008:

First came the V-amp 2, the one thing I actually bought for myself (for about $50, second-hand) back in 2008 since it had a ridiculous ratio of features to cost (and somehow still does): lots of mostly high-gain amp models, the ability to separately bypass the amplifier and cabinet simulations, the ability to separately configure the line and headphone outputs, MIDI in and out etc.

2010 brought a prettier enclosure for my DIY effects and some spray paint:

2014 edition:

In 2014 I added another entry-level multieffect to supplement what the V-amp is lacking (a Digitech Whammy, mostly) and a MIDI controller for faster access to all the presets I never used.

2018 edition:

By 2018 I had also bought an RP155, hoping it would have higher-fidelity (read ‘better-sounding’) models than the V-amp. It does not, but it does offer a vastly better implementation of the Whammy than the RP80 did, plus a whole bunch of other effects I’ll never use, so on the pedalboard it stayed. I also got a V-amp 3 in case the other one suddenly dies and to allow a separate ampsim/cabsim bus.

Fitting all this together required a touch more planning, so I took the time to build a proper clamshell type of box with all the inputs and outputs organized in one spot and conditioned by an I/O unit.

The Issue

Both the V-amps and RP155 offer a simple up/down control by default in order to scroll through presets and a two-digit display + some LEDs to identify the active one. So keeping track of them and jumping to any particular combination of presets and active individual effects became quite a chore. Well, to be fair all of this is completely unnecessary: I could just plug into a computer running Guitar Rig or BIAS FX and have higher-quality sims easily available, but anybody can do THAT. Somewhere in the last 12 years the goal shifted from having the most useful tools I could afford to obtaining the most diverse, interesting and inspiring sounds from the cheapest and least popular gear. And if nothing else, at least the Pandemic has afforded me some time to streamline the whole pedalboard experience.

So I would need a means to control two V-amps, the RP and some analog effects and maybe display what the active preset is about. Alright, I have LCDs, Arduinos, most of my standalone effects are electronic bypass, the V-amps have MIDI, the main hurdle is the RP155, which only has MIDI via USB and no other control interface that I could find on the board. But I did buy a Raspberry Pi Zero some time ago and it’s been busy gathering dust since I discovered it’s not powerful enough to run impulse response convolution without more effort than I was willing to invest.

The solution

The nexus of control for the latest pedalboard edition would be a unit I pretentiously dubbed the Lament Configuration: it houses the RP155 (sans enclosure) to save space, plus a tuner and the actual controlling bits consisting of an Arduino Pro Nano clone, Raspberry Pi Zero, 16x2 LCD and auxiliary...

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LC.ino

Lament Configuration V2 firmware (ESP32).

ino - 14.76 kB - 07/23/2020 at 20:13

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data.zip

SPIFFS data folder for Lament Configuration V2.

x-zip-compressed - 3.84 kB - 07/20/2020 at 19:47

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midi.ino

RP80 MIDI firmware (Arduino UNO).

ino - 2.54 kB - 07/20/2020 at 19:47

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latency.wav

Test to measure how much latency all the A/D and D/A conversions are adding. Looks like 6 ms tops.

Waveform Audio File Format (WAV) - 869.00 kB - 05/15/2020 at 08:45

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lamentconfig.ino

Lament Configuration V1 firmware (Arduino UNO).

ino - 9.37 kB - 05/15/2020 at 08:43

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  • The Big Update

    FiveseveN07/20/2020 at 20:05 0 comments

    So I did something silly: a couple of hours into configuring patches for the pedalboard I remembered I don’t actually like the sound of tubes and that an eight-button interface is fine for casually tweaking a preset but not much fun when you have to set 125 in one sitting. Sure, I don’t need a hundred presets and I was mostly done already but the idea had already taken over—I would use an ESP32 so I can configure everything with a web interface. And while at it, I also managed to squeeze in one more guitar processor instead of things I didn’t use.

    The RP80 took over the RP155’s job as pre-distortion effect provider, while the RP155 with its more extensive reverb and delay options has become the purveyor of “wet” effects.

    Does your head hurt too?

    Lament Configuration V2

    I had bought a couple of ESP32 modules for a future venture and since I had no previous experience with the platform I figured this could be a good learning opportunity. And not to have things too easy I also made it my first KiCad project.

    The ugly formatting and abundance of jumper wires are due to lazyness though, not my lack of experience with KiCad. Same reason I “surface mounted” the THT components: I loathe drilling tiny holes.

    I did finally buy a white-on-blue LCD that better fits the overall color scheme, so I guess the zero in “Zero Budget” has become about $10. Removing redundant information from the display allowed me to include a label for the ○ (function) button as well.

    Of course the one time I didn’t use IC sockets I got a dead channel in the level shifter talking to the LCD. So I connected the input straight to the 3.3 V output and it works just fine, indicating I didn’t need that shifter anyway. The PCB transfer didn’t come out great but it’s still better than protoboard.

    Believe it or not, it’s a lot more tidy.

    I got bogged down in firmware land for a week due to what I hear is called “premature optimization”, but once I realized the ESP32 has massive ammounts of RAM and storage compared to an ATmega328P everything went smoothly. The ESP-WROVER I used even has extra PSRAM that I didn’t touch. My programming education started in the 5th grade and ended in the 8th, so I’ve attached the code in case anyone wants to point out my mistakes:

    Lament Configuration V2 firmware and data folder.

    Now interface design is something more up my alley, and I hope I kept it simple and funcional:

    Clicking a bank from the left list loads its contents into the central table, where the 5 presets (and the bank’s name) can be edited at once.
    The list of RP155 presets serves as a reference and their new ultra-wide 6 character labels can also be edited here.
    Then the [save] button writes all the configuration data to SPIFFS in JSON format.

    Teaching an RP80 to speak MIDI

    First order of business for welcoming back this ancient processor was to give it a proper antique paint job.

    Then I implemented a very quick hack for a MIDI upgrade: an ATmega328P reads the display to find where it’s at and shorts either the Up or Down button to ground if the last received MIDI Program Change is different from the active preset. The RP80’s digits and LEDs are all multiplexed so I used a hex inverter to kind of clean up the signal. It probably could be done programmatically and I’ll probably try in the future but right now I’m squeamish to delve into port registers and interrupts and whatever else would be involved. The current solution can only do 9 presets but it preserves the original functionality and it’s not essential.

    RP80 MIDI firmware

  • The Analog Stuff

    FiveseveN05/16/2020 at 07:29 0 comments

    Patchbay

    The most trivial element of this build, motivated as I stumbled upon that 3 RCA socket assembly from an old SCART to A/V adapter. The plate was cut out of the same unidentified plastic (Delrin?) that makes up part of the Lament Configuration and covered with matte black vinyl.

    I/O unit 

    I’ve cut a bit off the PCB and enclosure because the initial preamp/buffer situation that required a separate 9 V supply was too much hassle. Original schematic with the removed preamp part shown in negative color:

    VU meter

    The movement from the cheapest analog multimeter, a custom-printed backing and a simple op-amp driver makes a bouncy needle toy.

    OD

    A fairly generic ‘three knob overdrive’ but all the knobs are ‘gain’ controls of sorts. The box had previously housed a distortion prototype but I had even less need for that than an overdrive, so here we are. The schematic is more of a guideline, as I ended up using 47 nF for C4, D1 is actually two antiparallel red LEDs and there’s an extra 1 nF cap across the ‘GAIN’ pot.

    DickButt

    A Raygun Youth Chaos Fuzz with minimal modifications like electronic bypass and a couple of extra selection modes. I was very fortunate to find a small 6 position rotary switch in some old BOSS pedal I cannibalized. The enclosure came from the tuner that now sits in the Lament Configuration, and since one non-latching footswitch has been sitting in my parts bin since 2014, I used it for some momentary fuzzy glitchy stabs.

    Tube Boomer

    One of if not the main purposes of DSP multieffects is to replace big heavy tube amps. But guitar players love to fetishize their gear and a rich mythology has been built around the Tube Sound and how digital (or analog solid state for that matter) simulations could never capture its mysterious essence. Not being one of them, I find myself free of such preconceptions. But I had already built a Soldano SLO type of preamp with two 12AX7s, along with its own power supply, for a different project that got shelved / redesigned. Since I had some room and apparently nothing better to do, I decided to cram it into the pedalboard. I made the aluminium enclosure out of a PC PSU and some wire mesh, but after fiddling with stuffed PCBs running at 300+ V with intermittent contacts and strained wires, I decided to adjust my plans. So “Might as well include this preamp since it’s basically done” turned into a week of frustration as I made the switching system twice and shifted to a hybrid design with one 12AX7 and one op-amp, similar to the Blackstar HT series. This left me with plenty of room for point-to-point wiring for even more mojo.

    The most interesting part of it is probably the switching: it’s powered by a separate 9 V supply (shared with the rest of the pedals), which allows me to turn off the tube PSU when I’m not using it (close to always). This prevents unnecessary wear on the heater and interference from the HV plate and high current heater rails while still passing the signal in bypass mode.

    Oh, and the name comes from this brilliant YouTube comment:

  • The Lament Configuration

    FiveseveN05/15/2020 at 15:39 0 comments

    The brains of this operation reside in this slightly wedge-shaped enclosure I built from acrylic (covered with auto window tint), MDF, some unidentified white plastic sheet, two hinges and a bit of aluminium:

    I also made the footswitches out of nuts and bolts and springs, since even the cheapest momentary stomp switch is about $2, and that multiplied by nine does not equal zero budget.

    The main board just haphazardly holds the LCD, Arduino and Raspberry Pi together, along with a 5 V regulator. This assembly is joined by the guts of a guitar tuner with a nice big display.

    The RP155 board is screwed directly to the particle board base of the pedalboard. Why is it missing the two‑digit display? Because I unsuccessfully tried to move it and made a mess of the pads and traces.

    Interface

    Half a sheet of A4 showing the extent of my planning:

    The V-amps have presets in sets of five (A through E) organized in 25 banks and the controller mimics this layout:

    - buttons ˄ and ˅ increment and decrement the current bank
    - buttons A, B, C, D and E recall the corresponding preset
    - button or or just * is for an assignable special function on each preset:

    • TAP : Tap tempo for time-based effects
    • VERB: Toggle reverb on/off
    • MUTE: Toggle mute for both V-amps (set to tuner mode)
    • M V3: Mute V-amp 3
    • M V2: Mute V-amp 2
    • FX : Toggle V-amp effects on/off
    • Rpbp: Toggle RP155 effects on/off
    • DET: Toggle V-amp ‘drive’ mode

    Since this function, the preset name and the state of the analog pedals need to be set and saved, a configuration mode was needed and it is accessed by pressing the ˄ and * buttons simultaneously:

    Here’s what the buttons do in edit mode:

    ˄ / ˅ = scroll preset name
    D / * = scroll RP preset
    A = cycle Tube Boomer mode
    C = cycle * mode
    E = save and exit edit mode
    B = exit without saving

    The state of the other controllable pedals (NR300 and SF5) is automatically read and stored when saving.

    And here’s the breakdown of the display:

    Main screen 

    NN BBBBBBBB RRRR 
     A PPPPPPPP MMMM

    Edit screen

    NN PPPPPPPP 
     A RRRR TT *MMMM

    N = Bank number
    B = Bank name
    R = RP preset number (shows ‘…’ while the Pi is booting)
    A = Preset index (A/B/C/D/E)
    P = Preset name
    M = * mode
    T = Tube Boomer mode

    The Raspberry Pi is essentially being used as a MIDI to USB bridge: all it does is read a MIDI input via ttyMIDI and pass it on to the RP155 USB MIDI port through an ALSA connection. It also sets a pin high to signal when it’s booted and ready. Why not do everything in the Pi? Because it takes a while to boot. By using DietPi and optimizing it to the best of my knowledge (which is not much, as this was my first project involving a Pi), I got it down to about 13 seconds. Which is less than what it takes for the 12AX7 in the Tube Boomer to heat up. The V-amps themselves take about 5 seconds to boot up, so I could probably make it work, but I’m more comfortable with the Arduino and I don’t mind the modularity.

  • An Overview

    FiveseveN05/15/2020 at 09:03 0 comments

    Indexed view of all the components:

    1. patch bay
    2. I/O unit
    3. Behringer CC300, a Dimension C clone
    4. Behringer V-amp 2
    5. Behringer V-amp 3
    6. PSU for Digitech RP155
    7. PSUs for V-amps
    8. PSU for the pedals and everything else
    9. PSU for CC300 and I/O unit
    10. PSU for Tube Boomer
    11. Power switch for Tube Boomer
    12. VU meter for input/DI level
    13. expression pedal for RP155
    14. Behringer NR300, an NS-2 clone
    15. Tube Boomer preamp
    16. DickButt fuzz
    17. DOOM overdrive
    18. Ibanez SF5, a Big Muff style fuzz
    19. Lament Configuration

    Signal flow diagram: 

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Discussions

Craig Hissett wrote 07/23/2020 at 21:50 point

I love this!

I've longed for a small little pedalboard with some kind of Pi/Arduino control.

I've pretty much completed a Pi based pedal which runs a port of the Mod Duo pedal software (it's on here), but I want to give something like this one a go too!

  Are you sure? yes | no

FiveseveN wrote 07/24/2020 at 14:30 point

Well I kind of missed the mark on the "small little" part. :) I was/am planning to use the Pi for DSP as well, since the RP155 also acts as an audio interface and it's already connected. Another goal for version 3, I guess.

  Are you sure? yes | no

Craig Hissett wrote 07/24/2020 at 14:53 point

That would be awesome dude. Yeah, the RP pedals can be really useful if they have that audio interface capability!

  Are you sure? yes | no

Pedro Henrique wrote 05/24/2020 at 22:12 point

One doubt I m trying to develop a midi switcher for Behrringer Vamp3,  Did you tryout controlling some effects and patch switching by MIDI in Vamp?

  Are you sure? yes | no

FiveseveN wrote 07/02/2020 at 19:56 point

Yes of course, that is the main point of the Lament Configuration controller. You can find the MIDI implementation chart on page 14 of the V-amp 3 manual.
And stay tuned, a big update is coming :).

  Are you sure? yes | no

Pedro Henrique wrote 05/24/2020 at 22:12 point

One doubt I m trying to develop a midi switcher for Behrringer Vamp3,  Did you tryout controlling some effects and patch switching by MIDI in Vamp?

  Are you sure? yes | no

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