Funbox - Open Source Guitar Pedal Platform, Stereo, Expression, and MIDI

I’d like to share something I’ve been working on, called Funbox (yes really, that’s what I named it :laughing:). It’s an open source guitar pedal using the Daisy Seed on a through hole PCB, with buffered stereo in/out, expression, and midi capability. The Kicad files for the pcb, along with some software I’ve developed for it can be found here:

And here is a demo video of one of the modules, called Mars (I have three more video demos coming for the other ones):

If anyone builds one please share! Especially if you run into any issues, I’d like to iron those out. There is a Tayda drill template linked in the github repo for the 125B size enclosure.


Always a great day when you post a new pedal project :guitar:
It’s sounding amazing and versatile! The addition of expression input looks like fun!

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A while back, there was some talk about noise with Rev 7 Seed - was anything special done for this, or does it ‘just work’?

@tele_player Yes, I used the low pass filter circuit from @kshep ‘s pedal design on the left and right output from the daisy seed (3k3 in the audio path at the Daisy audio out followed by a 2.2nF cap to ground).

I’m having a blast with the expression pedal! First time using one (it’s the Moog ep3) The control setup was somewhat inspired by how Meris pedals do it, where you can set the range on multiple controls.

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Beautiful! I like that you are sticking with trough-hole and the DIP switches are a very nice touch. Thanks for sharing, esp. the KiCad files.

(A minor point, Pluto is not a planet :laughing:)


Once a planet, always a planet!

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New Funbox demo, Neptune Reverb/Delay! This is very similar to my Atlas pedal, but better in my opinion since it’s stereo.


Here’s another demo, variable speed dual looper. It uses a modified DaisySP looper class to achieve the variable speed option, having lots of fun with this one! It’s running smoothly at 96kHz.


Looks super fun to play with!!
I personally dig how glitch-y it can get also :smiley:

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A response to your minor point, Pluto is a kind of a planet, specifically, it is a dwarf planet.

I use “is” as defined by Korzybski in General Semantics and his book Science and Sanity, 1933.

Science and Sanity full text at the European Society for General Semantics:

And now, back to Funbox - Open Source Guitar Pedal

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Perhaps Mr. Korzybski and Mr. Brown should get together and sort this out :slight_smile:

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Lol I’m just stuck in the 90s, I can’t let Pluto go!

This is a copy and paste from the pedalpcb forum, but wanted to add this info here as well. Short story is after building the 3.1 version of the Funbox pcb using a pcbway board, I was getting some weird noise on the right channel. I tried using different op amps and found one that fixed the problem and improved overall noise in comparison with the TL074, which was the MCP6024

And here’s that post:

“After some further testing with the MCP6024 quad op amp, I’m really pleased with the (lack of) noise level, compared with the TL074. I know noise has been an ongoing issue with the Daisy Seed in a buffered guitar pedal, especially with the rev 7. I’d be curious if the dual op amp version (MCP6022) lends any improvement for the Terrarium.

I’m mostly shooting in the dark, but a couple of things in the spec stand out from the TL072/TL074:
MCP6024 is rail to rail, and has a lower voltage range (2.5V to 5.5V). This lower voltage range would not do well for an analog pedal (much less headroom), but it works great for the Daisy Seed and it’s lower input audio voltage requirements. Gain bandwidth (10MHz vs 5.5MHz) and Slew Rate (7V/µs vs 13V/µs) are significantly different, but I don’t know what that means. Also, I noticed on the TL074, the minimum Voltage Supply Span is 10v according to the spec on the Digikey page. I’m only providing 5v power in the Funbox, so possibly I was using it out of spec? Assuming that means what I think it means.

I’ve tried the MCP6024 in the Funbox with a variety of outputs, going into a tube amp, into an audio interface, and directly into headphones, and all are very quiet in terms of noise.

Some of the other op amps I tried and their perceived results:

MCP6004: Same noise issue/level as TL074
MCP6274: Same noise issue/level as TL074
LM324AN: Much worse noise than TL074

Note that I’m not saying these are “bad” op amps, I’m only saying that in this particular circuit, in the Funbox, this is the result I got. I’m sure there’s a logical reason for each of these results, but my electronics/op amp knowledge it too limited to understand why. Any expertise from anyone on the topic of op amps would be greatly appreciated!”

On a completely unrelated note - the footprints of the OpAmp and R19 seems to overlap a bit. Is that intentional?

Yes, I squished them in there, it’s not perfect but I usually take the “good enough” design approach for this type of thing. You’ll find a few other places where courtyards overlap

Last module demo for awhile, a midi keyboard effect: