Sunday, December 12, 2010

Crushed Glass granular sampler/looper/glitcher

This is something I've been working on (on-and-off) since january or febuary of '10. For DIYers, looping is usually restricted to ISD sound recorder chips. They are neat but don't offer a whole lot of flexibility. I wanted totally random access to individual samples for some pseudo-granular drones so I saw what I could do with microcontrollers. Initially I had started learning dsPICs, but later put it aside and went with what I knew, the 8bit AVR.

I'm using SPI RAM which isn't the fastest solution but I just wanted to see if my ideas could be done. Fidelity was secondary. I went with the ATMEGA328 which is the chip with the most amount of internal RAM in DIP format. I didn't want to use the larger 40-pin DIPs.

I wanted to be able to ping-pong the "playback head" in as little time as a 1ms sample window, define start and end loop points, among other things. That meant quite a bit more code that simple record and playback. Keeping it tight, I still manage up to 12KHz sampling on the 8-bit uC. Considering there's a lot of SPI communication with both RAM chips and the DAC, I don't think that's too bad. Stuff like LED updates and potentiometer sampling only happen around 20 times a second. I use an additional uC (atmega88) on a daughter board for the 16 LEDs. It serves as a 4-to-16 decoder.

On the less technical side, sound-wise it is pretty lofi. It doesn't handle complex recordings well. Stuff like full chords, mixed-down songs, things with a lot of harmonic detail and smooth volume dynamics. Some complex things work, most don't. What it does handle well is individual monophonic instruments (or picking single strings on a guitar), some vocals, cicuit bend noises, and it handles electronic beats really well!

The controls are really counter-intuitive, and for this reason I won't be building these for anybody just yet. There are some bugs and limitations that I have not been able to fix in the weeks and months of work. The problem is that I designed this back-to-front which is a really bad way of doing things. I started building a looper then later tacked on features. It's all duck-taped and bandaided together with tricks and hacks in the code. What I should of done is figure out my features first, then design around that. Because I did the reverse, fixing the bugs and limitations have been so difficult that I'll have to start over if I intend to sell these. Personally I can live with these quirks, but I can't help but think others would be confused.

The next one will be much better!

A list of features/controls, some more technical information and a video below.

- Input gain (with red clipping LED)
- Independent Dry and Wet knobs
- Record / Playback toggle switch (with purple rec LED)
- Hard bypass toggle switch (with orange LED)
- Low pass filter
- 16 LED "head" position
- Speed, sets the samplerate
- Start and End realtime sample trimming
- Trim drift/gradual offset
- Confusion knob which does ping pong stuff to the "head"
- Direction knob sets forward or reverse, or glitchy in-between madness!

Main CPU: ATMEGA328 (overclocked to 12mhz at 3.3v)
Secondary CPU: ATMEGA88 (for 16 LEDs only)
ADC: internal 8bit
DAC: external 12bit MCP4921
RAM: two 23k256 ICs
LPF: MAX7403
Programmed in BASCOM

Thanks for reading/watching!


Anonymous said...

This looks mega awesome, right down to the paint job! I wonder how vocal samples would sound

Hodgman said...

I love it, especially like the led array which give you some feedback of what it is doing and i must say i feel like it is a very straightforward and easy to understand design you have there..i think it is one of the most interesting loopers out there actually..and i long to get my hands on one..or a kit maybe..

Faldoe said...

Tape!!! As always. This is freakin AWESOME!!!! your stuff gets wackier and wackier. You gotta build some more of these. Keep it up man.

nychthemeron said...

goddamnit e

why do you do these things

why are they so crazy

how do you do it without killing yourself

Success said...

I wish I were half as skilled and creative as you are. I have at best attempted to dismantle a broken electronic device, only to reassemble it and discover that I have several pieces remaining. Never a good feeling :(

Unknown said...

I love this design - you did a great job, and it's beautiful also. I'd love to see the schematics etc and the code...

trikome said...

awesome.. some great granular sounds :D

SPIKE the Percussionist said...


The Dildo Factory said...

Will you be building and selling any more of these??? I'm rather interested in one if you are.

Anonymous said...

I would pay good money for this. Please e-mail me ( and let me know what you're planning to do with this model and/or design(:


Anonymous said...

hello, congratulations for your work.. this pedal is brillant.....are you selling this? i want one.... thanks

Anonymous said...

Nice work! Please send a mail to when it's ready for sale

noise_head said...

Hi, man, have you made a new version of this thing? i'm very interesting in buying it. my e-mail:

Anonymous said...


i'm very interesting in buying it!

mail,,,,,,,,, (

thank you


Jefferson Relic said...

guess this project is dead? im also interested..