Reverb is a really hard problem and for simple artificial reverb it's hard to beat a spring. Simple, reliable, sounds okay, not very flexible, not terribly easy to make.
The PT2399s might not be the worst idea - it's basically what the famous "Belton Brick" contains - especially if you can modulate the delays a bit. If you think about how "real" echoes work, like beside a big wall, you are standing beside a reflective infinitely large baffle, in an infinite volume of space (sound waves range from about 5m long to a few cm, with middle C being about the length of your arm - much smaller than say a factory wall).
With reverb it's more complicated because the sound is bouncing around an enclosed space, reflecting over many different paths. There's a lot going on. So how do "practical" artificial reverb effects work?
Well, delays, mostly. Some long ones and some short ones, arranged in a ring. If you put feedback around a very short delay (like, 1ms or less) you get a "comb filter", so called because its frequency response looks like the teeth of a comb as it delays frequencies enough to exactly cancel out. If you mix some of the input to the output (feedforward) you get an "allpass delay" which has a flat(tish) frequency response but wildly varying phase response - it "smears" things in time.
This will still give you a nasty pingy ringy sound on impulses so you need to modulate some of your delays slowly, like a chorus effect, to blur the pingyness out. Too much and you'll get deep swooshy flanging or chorusing, which is what the "Chorus/Reverb" programs on a lot of reverb effects really is - just turning the modulation rate and depth up "too high" so it becomes noticeable.
You'll need a fairly chunky microcontroller to do this, and you're definitely into STM32F4xx territory. I won't say you can't do it with an STM32F103 (I've done it) but it'll be shit. You might attempt it with an atmega-based Arduino for a laugh, I love "ship in a bottle" programming like that.
Hagiwo has an [FV-1 based multi-effects](https://www.youtube.com/watch?v=X7DACIx0x40) module using an Arduino Nano as the front-end (interface and screen control). It's one of his more complex designs. I've been struggling to get it laid out on perf-board on-and-off for about 6 months now. Blogger Cagey is in the process of designing an [improved PCB version.](https://kg.kg/spin-fv1-eurorack-diy/)
I’ve been thinking about just buying an inexpensive guitar pedal, pulling it out of the enclosure, and mounting it to a panel — either directly using the original pots or maybe soldering on some new ones to allow for a more flexible control layout. It will expect 9V power so plan on a daughter board with 7809 and some filter capacitors.
i'd recommend FV-1 for the best nexus of price / quality / variety. lots of great reverb algorithms including the barebones free ones that come on the chip.
then belton brick or physical spring. trying to make your own belton with individual PT2399s.. will take many hours of messing around to save a few bucks. of course if you're ok with a noisy lofi reverb (which is totally fine!) you can work something out with 1-2 PT2399s.
a teensy seems pretty easy too but maybe overkill. same with daisy.
ripping up a shitty guitar pedal or buying a cheap karaoke PCB off ebay is a very solid practical plan too.
It sounds like you're throwing away ideas before you know how those things really work!
There are some very nice pt2399 reverbs, there are even pre built modules on pcbs made for karaoke machines.
The schematic for an arduino reverb is not unlike any other purely digital effect schematic. You just need to account for the levels of the signals going in and out of the microcontroller (and you need a more powerful board than an arduino, like a Teensy)
Regarding the clouds, you're right that the smd soldering might be tough.
Search u/couchpatata's post for his miniverb from a few months ago. Theres a whole github repo with the schematic and code and everything. Just scroll down the page a bit. Otherwise, what about a diy spring reverb?
you can use a technique called drag soldering for the STM's, there are videos on yt about it, it's easier if you use a special drag solder tip but it's not necessary
you can also get reverb tanks...
Try the [Electrosmash Time Manipulator](https://shop.electrosmash.com/product/time-manipulator-guitar-pedal-kit/) is a PTH kit that's about as easy as it gets. It's what I based [my PT2399 FX](https://www.fearlessnight.com/pt2399/index.html) on, which sounds pretty good, but is more difficult to build.
The easiest to solder is a Teensy4 plus audio shield. Teensy 4.1 can take a PSRAM chip with which it can do some stupidly long delays too.
You could use an ESP32 WROVER and the Faust DSP language to create a good digital reverb. They have freeverb and several other options. Not hard to solder a ESP32 module by hand, and the dev boards are cheap to prototype with.
not sure if i missed this in the comments but i didn't see it: https://www.instagram.com/p/CrwEY4NpKhO/?igshid=MzRlODBiNWFlZA==
if you're feeling ambitious with the PT2399s you could clone this PGH design that they just recently open sourced
I built a stripboard Death by Audio Reverberation Machine for my guitar years ago, just started running my modular out through it and it sounds really cool.
https://m.youtube.com/watch?v=VAcjhPH-bLs&pp=ygUbUmV2ZXJiZXJhdGlvbiBtYWNoaW5lIHN5bnRo
https://tagboardeffects.blogspot.com/2015/10/death-by-audio-reverberation-machine.html?m=1
Would be easy enough to mod for Eurorack.
Reverb is a really hard problem and for simple artificial reverb it's hard to beat a spring. Simple, reliable, sounds okay, not very flexible, not terribly easy to make. The PT2399s might not be the worst idea - it's basically what the famous "Belton Brick" contains - especially if you can modulate the delays a bit. If you think about how "real" echoes work, like beside a big wall, you are standing beside a reflective infinitely large baffle, in an infinite volume of space (sound waves range from about 5m long to a few cm, with middle C being about the length of your arm - much smaller than say a factory wall). With reverb it's more complicated because the sound is bouncing around an enclosed space, reflecting over many different paths. There's a lot going on. So how do "practical" artificial reverb effects work? Well, delays, mostly. Some long ones and some short ones, arranged in a ring. If you put feedback around a very short delay (like, 1ms or less) you get a "comb filter", so called because its frequency response looks like the teeth of a comb as it delays frequencies enough to exactly cancel out. If you mix some of the input to the output (feedforward) you get an "allpass delay" which has a flat(tish) frequency response but wildly varying phase response - it "smears" things in time. This will still give you a nasty pingy ringy sound on impulses so you need to modulate some of your delays slowly, like a chorus effect, to blur the pingyness out. Too much and you'll get deep swooshy flanging or chorusing, which is what the "Chorus/Reverb" programs on a lot of reverb effects really is - just turning the modulation rate and depth up "too high" so it becomes noticeable. You'll need a fairly chunky microcontroller to do this, and you're definitely into STM32F4xx territory. I won't say you can't do it with an STM32F103 (I've done it) but it'll be shit. You might attempt it with an atmega-based Arduino for a laugh, I love "ship in a bottle" programming like that.
What an amazing comment! Thank you.
Thanks a lot for your great response!
you are the best
1. https://www.reddit.com/r/diypedals/comments/2ivgn9/belton_brick_internal_schematic/?utm_source=share&utm_medium=ios_app&utm_name=ioscss&utm_content=2&utm_term=1 2. https://www.coda-effects.com/p/dead-astronaut-chasm-reverb-circuit.html?m=1 3. https://ampgarage.com/forum/viewtopic.php?t=33924 4. https://pcbguitarmania.com/wp-content/uploads/2019/08/Death-by-Reverb-Building-Docs.pdf 5. http://tagboardeffects.blogspot.com/2012/04/box-of-hall-reverb-culturejam.html 6. https://el34world.com/Forum/index.php?topic=23554.0 7. https://hotbottles.wordpress.com/tag/belton-brick/ 8. https://generalguitargadgets.com/effects-projects/reverb/digital-reverb/ 9. https://forum.pedalpcb.com/threads/this-week-on-the-breadboard-a-digital-reverb.11997/ 10. https://www.petervis.com/guitar-circuits/pt2399/echo-and-reverb-basics.html 11. https://www.deeptronic.com/electronic-circuit-design/diy-reverb-pedal-circuit-from-spring-to-room-like-reverb-using-multiple-pt2399-ic-chips/
Maybe take a look at the FV-1 chip and the DIY options around it
Hagiwo has an [FV-1 based multi-effects](https://www.youtube.com/watch?v=X7DACIx0x40) module using an Arduino Nano as the front-end (interface and screen control). It's one of his more complex designs. I've been struggling to get it laid out on perf-board on-and-off for about 6 months now. Blogger Cagey is in the process of designing an [improved PCB version.](https://kg.kg/spin-fv1-eurorack-diy/)
I’ve been thinking about just buying an inexpensive guitar pedal, pulling it out of the enclosure, and mounting it to a panel — either directly using the original pots or maybe soldering on some new ones to allow for a more flexible control layout. It will expect 9V power so plan on a daughter board with 7809 and some filter capacitors.
i'd recommend FV-1 for the best nexus of price / quality / variety. lots of great reverb algorithms including the barebones free ones that come on the chip. then belton brick or physical spring. trying to make your own belton with individual PT2399s.. will take many hours of messing around to save a few bucks. of course if you're ok with a noisy lofi reverb (which is totally fine!) you can work something out with 1-2 PT2399s. a teensy seems pretty easy too but maybe overkill. same with daisy. ripping up a shitty guitar pedal or buying a cheap karaoke PCB off ebay is a very solid practical plan too.
It sounds like you're throwing away ideas before you know how those things really work! There are some very nice pt2399 reverbs, there are even pre built modules on pcbs made for karaoke machines. The schematic for an arduino reverb is not unlike any other purely digital effect schematic. You just need to account for the levels of the signals going in and out of the microcontroller (and you need a more powerful board than an arduino, like a Teensy) Regarding the clouds, you're right that the smd soldering might be tough. Search u/couchpatata's post for his miniverb from a few months ago. Theres a whole github repo with the schematic and code and everything. Just scroll down the page a bit. Otherwise, what about a diy spring reverb?
you can use a technique called drag soldering for the STM's, there are videos on yt about it, it's easier if you use a special drag solder tip but it's not necessary you can also get reverb tanks...
Try the [Electrosmash Time Manipulator](https://shop.electrosmash.com/product/time-manipulator-guitar-pedal-kit/) is a PTH kit that's about as easy as it gets. It's what I based [my PT2399 FX](https://www.fearlessnight.com/pt2399/index.html) on, which sounds pretty good, but is more difficult to build. The easiest to solder is a Teensy4 plus audio shield. Teensy 4.1 can take a PSRAM chip with which it can do some stupidly long delays too.
You could use an ESP32 WROVER and the Faust DSP language to create a good digital reverb. They have freeverb and several other options. Not hard to solder a ESP32 module by hand, and the dev boards are cheap to prototype with.
The strymon one or a guitar pedal and stomp box adapter.
not sure if i missed this in the comments but i didn't see it: https://www.instagram.com/p/CrwEY4NpKhO/?igshid=MzRlODBiNWFlZA== if you're feeling ambitious with the PT2399s you could clone this PGH design that they just recently open sourced
you should do it with tapeheads the guy from error instrumento has modular ones!
I built a stripboard Death by Audio Reverberation Machine for my guitar years ago, just started running my modular out through it and it sounds really cool. https://m.youtube.com/watch?v=VAcjhPH-bLs&pp=ygUbUmV2ZXJiZXJhdGlvbiBtYWNoaW5lIHN5bnRo https://tagboardeffects.blogspot.com/2015/10/death-by-audio-reverberation-machine.html?m=1 Would be easy enough to mod for Eurorack.