Author Topic: So ya wanna build a High Def Raspberry Pi based multi-effects unit?  (Read 501 times)

treefall

Over a year ago I set out to do that.  I found modep which ports the opensource MOD (MOD Devices) pedalboard software to Raspberry Pi.  Wasn't too long before I had a prototype with 24-bit/96khz audio, 4-cores of CPU allowing a dozen or more of the 350+ LV2 plugins to run in a virtual pedalboard.  It sounded great and I could string together virtually any pedalboard imaginable.

I wanted a stage worthy device though, so I added an LCD along with assignable footswitches, knobs, expression, midi, even phone control (via osc)

I shared it with some friends who loved it and it soon became obvious, I should share the project with others.  After many prototypes and issues trying to get enclosures made, I'm making it available to other DIY pedal builders.  Two others have built it successfully so far.  Two more have ordered parts.  I'm looking for 7 more builders before I order another round of circuit boards.

You can check it out the details here: https://treefallsound.com
 


Here's what that pedalboad looks like through the MOD web UI (connected via wifi):



Marcvv

Re: So ya wanna build a High Def Raspberry Pi based multi-effects unit?
« Reply #1 on: September 12, 2020, 02:09:12 AM »
Wow, Rand, this looks amazing. What an investment you made in the project itself but also your website about the pedal. i might be interested in building one. The website shows the store but there is no price and shipping info?

Cheers, marc
Transfering graphics onto a stompbox using the Dark T-Shirt Transfer method
http://www.marcvanvugt.com/articles.php?id=11

potul

Re: So ya wanna build a High Def Raspberry Pi based multi-effects unit?
« Reply #2 on: September 12, 2020, 04:27:22 AM »
This is a very interesting project, very similar to an unfinished project I have myself in a drawer.

Although I will probably start tinkering with it, I'm not interested in the whole enchilada kit. I already have a bunch of parts I will reuse and I'm not yet interested in the enclosure (I already have a stage worthy HX Stomp, I want this just for the fun of DIY).
Any chance to get individual parts instead?

My first intention is to test the whole thing with parts I have laying around, and if I'm convinced I might go for the "ready to gig" version. I'm evaluating what parts I can reuse..... so I have a couple of questions:

-Will it work with a model B board instead of the model A+? (aside from the form factor)
-Are you using the touch buttons of the Pimoroni display for something, or can I use another I2C/SPI display instead?
-Any specific reason you are using the Audioinjector audio board? Any experience with other audio boards?
-Are the encoders connected directly to the GPIO pins of the Pi, or is there any interface in the middle?
-Is your custom sofware all programmed in python?




The website shows the store but there is no price and shipping info?

Cheers, marc

If you click the banner you will go the the product details. 88$. No shipping info though


Marcvv

Re: So ya wanna build a High Def Raspberry Pi based multi-effects unit?
« Reply #3 on: September 12, 2020, 07:38:37 AM »




The website shows the store but there is no price and shipping info?

Cheers, marc

If you click the banner you will go the the product details. 88$. No shipping info though
[/quote]

Ah, i missed that. Thanks
Transfering graphics onto a stompbox using the Dark T-Shirt Transfer method
http://www.marcvanvugt.com/articles.php?id=11

treefall

Re: So ya wanna build a High Def Raspberry Pi based multi-effects unit?
« Reply #4 on: September 12, 2020, 11:47:43 AM »
Thanks for your interest.  Below are some answers...

The website shows the store but there is no price and shipping info?

Sorry I didn't make that more obvious.  I will.

There are two sets of parts you'll need to build a pi-Stomp.
1) Commodity parts from Mouser.com. The wiki includes a link to the BOM.  The current price for that is $106
2) The pi-Stomp custom parts (Circuit board and enclosure) and parts that Mouser doesn't carry (footswitches, audio card, LED halos, etc.)  My bundle on treefallsound.com is $88.  Shipping is USPS flat rate within the US and should be around $8.60

So bottom line.  Look to spend about $215 to $220 depending on shipping and taxes.


Any chance to get individual parts instead?

I'll likely offer that eventually, but understand it's not my mission to be a store.  I created a store to offer the custom circuit boards and enclosures but realized to save others from souring parts from 4+ locations and incurring shipping with each, I could stock those parts myself and allow builders to just make 2 orders (Mouser and Treefallsound).  I'm currently offering everything at cost to get people to build a pi-Stomp.  Everything on my store except for the circuit board and enclosure can be purchased from guitarpedalparts.com, smallbear-electronics or amazon.com

If there is demand for specific individual parts, I'll certainly try to offer that so lemme know what you'd like.


-Will it work with a model B board instead of the model A+? (aside from the form factor)
-Are you using the touch buttons of the Pimoroni display for something, or can I use another I2C/SPI display instead?
-Any specific reason you are using the Audioinjector audio board? Any experience with other audio boards?
-Are the encoders connected directly to the GPIO pins of the Pi, or is there any interface in the middle?
-Is your custom sofware all programmed in python?

I appreciate you wanting to build your own hardware.  All of the pi-Stomp specific software/firmware is python and designed with the idea that the hardware platform might be different.  All major components (footswitches, encoders, pots, LCD, etc.) have classes which can be instantiated (or not) or subclassed (https://github.com/TreeFallSound/pi-stomp/tree/master/pistomp).  Theoretically, you should be able to create your own python module for Your hardware in place of 'pistomp', and replace the 4 corresponding import references in https://github.com/TreeFallSound/pi-stomp/blob/master/modalapi/mod.py

Yes, pi-Stomp works great with a model 3 B board.  The A+ was chosen to fit inside a smaller enclosure.  It'll even work with a Pi Zero, though in my experience, with a single core and slower clock speed, it'll start to choke with more than 3 or 4 effects in a pedalboard.  Still, pretty cool and compact.

The touch buttons on the Pimoroni LCD are not used.  You can use other SPI displays and you'll notice in the github repo, I have basic driver subclasses for 4 other displays that I tried.  The pi-Stomp circuit board includes pads for a 10 pin header for connecting an alternate LCD.

I chose the Audioinjector Zero for two main reasons.  Form factor and because there really aren't many cards available with audio in (ADC).  The other two I found at the time both worked fine:
1) AudioInjector Stereo (larger, more expensive, no real advantage other than it comes with a stackable header and volume controls (oddly mounted perpendicular to each other)
2) HiFiBerry DAC+ ADC.  It worked just fine, but at nearly 3-times the cost and twice the size...
Note that the AudioInjector from treefallsound.com has a 2x20 header pre-installed.  If you buy from amazon, etc. you'll have to get and install your own.

The encoders incorporate two switches (the rotary switch and the push switch).  The rotary switches are connected directly to GPIO pins.  The push switches are go thru the Control ADC which is used to interface with the analog pots ("Tweak knob" and Expression pedal).  I did this because I found I could mitigate switch bounce issues better going thru the ADC versus direct to GPIO (and I was running low on GPIO pins but had 6 spare ADC channels ;-)



MetalGuy

Re: So ya wanna build a High Def Raspberry Pi based multi-effects unit?
« Reply #5 on: September 12, 2020, 02:49:31 PM »
Hi,

Very interesting project. On the second picture I see "SIMULATOR". I assume IRs or else?

treefall

Re: So ya wanna build a High Def Raspberry Pi based multi-effects unit?
« Reply #6 on: September 12, 2020, 04:19:34 PM »
Hi,

Very interesting project. On the second picture I see "SIMULATOR". I assume IRs or else?

Thanks.  So the base set of 358 plugins that the pi-Stomp setup script pulls includes 16 "Simulator" plugins.  I don't believe any are Impulse Response.  But, if you google: LV2 "impluse response" you'll find that they do exist and likely they might work.  It's on my ToDo list to try one or more.

The 16 Simulator plugins that the setup script pulls are mostly from the modep module:
https://pedalboards.moddevices.com/plugins?text=simulator&random=772f25ebdb964a549300befddc8ad8b0

Including:

CAPS: AmpVTS, CabinetIII, CabinetIV, Tonestack

Guitarix: GxAlembic, GxAmplifierX (mono & stereo), GxStudioPreamp (mono & stereo),  GxCabinet, GxSVT, GxUltraCab

MDA: Combo amp, Leslie

setBfree: Whirl

TAP: Tubewarmth

Marcvv

Re: So ya wanna build a High Def Raspberry Pi based multi-effects unit?
« Reply #7 on: September 13, 2020, 04:42:06 AM »
Thanks for the extra info. Would you be willing to ship to europe and how much would that be?
Transfering graphics onto a stompbox using the Dark T-Shirt Transfer method
http://www.marcvanvugt.com/articles.php?id=11

Firesledge

Re: So ya wanna build a High Def Raspberry Pi based multi-effects unit?
« Reply #8 on: September 13, 2020, 05:12:48 AM »
Interesting. What is the typical round-trip latency achievable with a moderately-loaded patch? How about the (measured) SNR?
Pédale Vite, multi-FX pedalboard

pruttelherrie

Re: So ya wanna build a High Def Raspberry Pi based multi-effects unit?
« Reply #9 on: September 13, 2020, 01:54:07 PM »
Nice project!

Thanks for your interest.  Below are some answers...
If there is demand for specific individual parts, I'll certainly try to offer that so lemme know what you'd like.
The main pi-Stomp board :)

Does it work with a Pi 4?

Also interested in the latency...

treefall

Re: So ya wanna build a High Def Raspberry Pi based multi-effects unit?
« Reply #10 on: September 13, 2020, 04:33:46 PM »
Some more answers...

Nice project!

Thanks for your interest.  Below are some answers...
If there is demand for specific individual parts, I'll certainly try to offer that so lemme know what you'd like.
The main pi-Stomp board :)

Does it work with a Pi 4?

I will definitely sell the main pi-Stomp board individually on treefallsound.com.  Right now, I just have 6 remaining and I'd like to have a few more completed builds reported before I order a new batch.

I have not tried it with a pi-4.  I don't see why it wouldn't work (it works with all pi-3's and Zero), but suffice to say, a pi-4 won't fit in the enclosure.

Interesting. What is the typical round-trip latency achievable with a moderately-loaded patch? How about the (measured) SNR?

Latency depends on the sound card settings (buffer-frames, sample-rate and periods).  I find I can run smaller pedalboards (say 7 or fewer effects) with the following (frames / rate) * periods:
( 128 / 96000 ) * 2 = 2.67 ms
( 128 / 96000 ) * 3 = 4.0 ms

For larger pedalboards or ones that use a lot of CPU intensive effects (modelers, etc.) I'll switch the frames to 256 from the MOD UI:
( 256 / 96000 ) * 2 = 5.33 ms

or bump down to 48kHz
( 128 / 48000 ) * 2 = 5.33 ms

This week, I'll try to get some actual measured latency numbers.  Some of the less-well coded effects do have noticeable latency.  Most, I'm fairly impressed with.

Regarding Signal to Noise Ratio... My scope died a couple of months ago (got a replacement pico-scope arriving in two days;-). but here is what I measured using a soundcard.  Each channel is running through 12+ feet of cable and a patchbay so I'm sure the real SNR is better (I'll re-measure with my new scope this week).

You can see at the bottom of the screen capture, S/R~=86 dB going thru the audio card:



When true-bypassed, S/R~=90 dB:



So it's probably safe to conclude the S/R thru the audio card is about 4dB worse than when bypassed.





micahvdm

Re: So ya wanna build a High Def Raspberry Pi based multi-effects unit?
« Reply #11 on: October 18, 2020, 12:37:53 AM »
Hey Rand, such an awesome job!! Quick question, any chance you’ll be willing to share the schematics? Only reason I ask is that I have most of the parts on hand and I’d like to give a free wired version a go to test everything out.

treefall

Re: So ya wanna build a High Def Raspberry Pi based multi-effects unit?
« Reply #12 on: October 18, 2020, 01:58:06 PM »
I'm totally willing to share portions of the design to get someone going on their own.  If there is a certain part of the system you're interested in, send a personal request (support@treefallsound.com) and I'll try to help.

One thing I do plan to make available soon is the GPIO pinout for the raspberry pi.  That should enable others to know which pins to use when using the pi-Stomp software.  In the meantime, you can probably figure most of that out from this piece of code: https://github.com/TreeFallSound/pi-stomp/blob/master/pistomp/pistomp.py

As you may have seen in the pi-Stomp FAQ, it has always been my intention to encourage Full DIY, and I do plan to open source the full hardware design eventually.  In the short term though, there are a number of reasons I feel the need to keep the full schematic and layout to myself:
  • I believe the hardware design needs to stabilize before it "forks".  I'm on my 7th iteration, with the last 2 iterations having multiple successful builds by others.  It seems that the latest iteration, to be made available this coming week, might finally be "there".  Still, I'd prefer a few more builds to be logged, and make sure that hardware bugs aren't lurking before others start making their own spinoffs.
  • For better or worse (ok, worse), I chose Fritzing to do the schematic/PCB design.  Fritzing appears to no longer be supported, and I'm maxing out it's capabilities.  Before open sourcing the hardware, I'd prefer to migrate the design to another tool (likely KiCad, but open to suggestions).  That will require some time to migrate.
  • In addition to all my time, I've invested about $3000 in enclosures, PCBs, and parts for the bundles I'm selling.  My margin is almost nil, but I need to recoup at least most of that investment before I enable someone else to steal my thunder.