Well, if you want to have no colouring of the sound in the preamp here then a circuit with negative feedback like a typical opamp circuit is the way to go.
There are very nice circuits with njfets which do not need a daisy seed to emulate a Guitar preamp. A favourite of mine is Son of Ben. Son of Ben Preamp - PedalPCB.com
1 Like
Note: KiCad runs on Mac,Windows and Linux, and it’s free.
Note also: guitar amps and speakers are effective lowpass filters, but two caps and two resistors isn’t a bad idea.
Made a video about this project and some of the effects I have running on it, been having a blast using it!
I compiled all of the modules shown in the video into this release: Release 125B OLED Pedal - Module Collection · GuitarML/DaisySeedProjects · GitHub
For the “effects-suite” you’ll have to use the bootloader to load to SRAM, which I thought was going to be complicated until I actually did it, and it turns out to be super simple, here’s the docs for it: libDaisy: Getting Started - Daisy Bootloader
If you try them out let me know what you think!
4 Likes
awesome. thank you. final parts for my 5 on the way. looper? seems elements are there to try an emulate what the EHX 9 series does.
Interesting, I think the input / output stage buffers could be improved in this design. After talking with ES, they also might be the reason there is some extra noise when using Rev7 seeds. I’m not an EE, I mostly just cobbled together this design from other schematics and designs, so it’s a bit out of my league to know how to improve upon the buffer design. If you have any ideas, I’m definitely all ears! I’ll have to PDF the full schematics later, but here are some screenshots of the Input / Output buffer circuits. These designs are the same as from the ES Daisy Petal reference designs.
Thank you for the schematics!
What I would certainly make differently: I would place a C in parallel to R6, because the voltage divider will propagate all noise from the +5V isolated rail directly into the signal. This would explain the noise at point B in your setup of 23.11. in this thread: Rev5 seed producing ~13dB higher noise floor - Electrosmith Products - Daisy Forums (electro-smith.com)
1 Like
Nice to see the pedal project reaching a wider audience! I expect @kshep will be getting a lot of order requests…
Hello! Just wanted to thank @kshep as well for open sourcing this project! I finally got the chance to complete this first build last night.
I didn’t catch that you could order the DC/DC converter through JBL before ordering assembly, so I ended up purchasing this separately, and soldering the part with an iron. I forgot how difficult it is to hand solder at a smaller smd pin pitch 
Otherwise, the build was smooth for most part (it was a definitely a tight squeeze for soldering some of the components), I made some mistakes with getting the pots/lcd screen flush with the case, but this was my first pedal build ever, and I have 4 more pedals to build where I can improve 
For this pedal, I am using the Rev 4 daisy with the original audio codec and am happy to say that, the noise level was astonishingly low, if not negligible. At least this is the case when I feed line out from my audio interface to the input, I’m sure that signal from my guitar or bass will have a different impact as the signal has a much smaller magnitude.
I can’t wait to implement some FX ideas that I have been looming on for the past year and I’m so excited that I was able to get this up and running without many hiccups. Thanks again for releasing this platform and reigniting my interest in audio DSP!
5 Likes
I bought the Petal years ago intending to build something but saw recently that it’s no longer available and the only docs are under Legacy Products 
. So I wasn’t sure where to start with it and have been looking around recently because I want to build pedals now. I’m so glad you made this awesome platform, well done!
@Transient Awesome, glad you were able to get one built! I feel your pain on hand soldering the DC/DC converter, that can be really tough. I did that on a my first few ordered before I could figure out how to get JLC to assemble them. Glad to hear you got everything working and I look forward to seeing what you do with it!
@eno Thanks! That’s one of the reasons I started this project was because the Petal wasn’t available any more. Your Daisy Petal should still function just fine though. There isn’t really any thing much different in developing for it vs my pedal. You could probably pretty easily even create a Daisy Petal hardware definition for my Software platform get some effects up and running quickly.
1 Like
Thanks for this suggestion!
I just tweaked my design and added a lowpass RC filter before the output buffer, totally cleared up the noise issue I was having.
2 Likes
Hello @kshep,
I’m currently implementing a stereo delay (currently a multi tapped delay with pitch shift control on each tap because I saw there was already an extensive reverb/delay module), and have a rough demo working but would like to expand more and flush out some details before sharing.
I have a question regarding the knobs parameter/adc scaling resolution: I can see that these are scaled from 0 to 127.
Is this design choice for ease of implementation to fit in the MIDI CC value range, or due to preserve accuracy in the ADC, or some limitation (or simply to accommodate the default value) in libDaisy with getting 16 bit resolution from the ADC?
If this is simply ease of integration into MIDI spec, I would like to propose an extension to the parameter type definition to give the option to specify parameters that occupy 2 midi CC slots and scale for 14 bits. Let me know if this makes sense and if you’d like to me make a PR to suggest an implementation to accommodate this feature and maintain current behavior so that no end user needs to change their effect classes?
@Transient Oh awesome, sounds like a fun project!
You are correct, the storage of parameters as u_int8 0…127 values was simply the quickest way to get this up and running and have it map to the midi cc parameter ranges. It’s my intension to improve this aspect, but I haven’t gotten around to it. There is no technical reason the way parameters are stored internally needs to be limited to midi range, and it would open up a lot more flexibility if I could support more types.
I touched on this issue a bit in the repo under the following tracked issue: Guitar Pedal Settings Storage is currently limited to 8 active effects with 16 parameters each · Issue #13 · bkshepherd/DaisySeedProjects · GitHub
I’m not sure when I’ll have time to actually make these improvements though. Hopefully something I can tackle sooner rather than later.
2 Likes
has anybody got the effects suite bin to flash?
the article sited is not specific and superfluous for a beginner.
and source code does not include items listed.
1 Like
Can you describe a bit more specifically what you tried? Once you’re cd’d into the Software/GuitarPedal directory of the main git repository, you should be able just to run make clean && make && make program-dfu to build the firmware and flash the Seed.
Let me try to clarify:
Source code for the effects suite is under the “effects-suite” branch of the GuitarML fork (not “main”). Switch to that branch, update submodules, build, then follow these instructions:
1 connect the daisy seed as normal, hold boot/reset like you would normally to upload to flash.
-
Run “make program-boot” to upload the bootloader to flash.
-
Press and let go of reset button, quickly press and let go of boot button. Should see sinusoidal led.
-
Run “make program-dfu” to have the bootloader upload the effects-suite binary to SRAM.
To be honest I’ve think I’ve only done it this way, building from scratch, and not using the pre compiled binary in my releases. I assume it’s trivial but just haven’t done it yet.
Hope that helps!
im trying to upload the effects suite bin file Keith Bloemer has provided…
i feel there are assumptions in directions on this site leaving out critical info.
“switch to the branch with the effects suite” already said i couldn’t find it…
step 1, fine…
step 2 Run “make program-boot” to upload the bootloader to flash.
from where?.
Owner@troy-PC MINGW64 ~/~/Desktop/GuitarML (main)
$ make program-boot effects_suite_125B_OLED_SRAM.bin
make: *** No rule to make target ‘program-boot’. Stop.
sorry got my enclosures and was anxious to get out and test today at my jam…
I think this merits a short video tutorial, stand by!
I found an easier way to do the bootloader/SRAM process, here is a quick and dirty tutorial video:
It’s currently an unlisted video on YouTube, but feel free to share the link if anyone might find it helpful. Read the video notes for further information and links to the GitHub page and Daisy Web Programmer. I also added a link to the web programmer on the GitHub releases page.
2 Likes
Keith’s solution with the web tool works great - if you want to use the command line, you’ll need to install the Daisy toolchain. Make sure you also modify the variables in the Makefile to point to your installations of libDaisy and DaisySP. (The Makefile in the repo relies on a Makefile inside libDaisy which defines the program-boot target; if you’re getting that error then libDaisy probably isn’t being found).