DIY DSP around the corner this time

[Peter Snowberg]

Hi all,

I've been flapping my gums about this one for about 2 years now, but finally it's about to see the light of day.

Many of you noticed that I recently took a couple of months away from forum. While I didn't talk much on-line during that time, I did work on my DSP project every single day.

The designs have gone through a lot of territory, but now it looks like they're finally as stable as they're going to get. So much of the cost with these things is in the DSP support and not the DSP itself. The box, knobs, microcontroller, memory, A/D/A, opamps, etc. make up so much of the cost that it was looking like it would make little sense to build an underpowered effects box when at the hacker level it could be three times as powerful for another $15 in chips.

In the end... we now have the beginning. If this first box takes off, there will be three, possibly four more in the series. I'm going to start out with a design that I have titled "Lotus".

The Lotus is actually a simplified user interface version of another design called "Soma" so I'll refer to the Lotus as using the Soma DSP architecture. Lotus is composed of 5 computers crammed into a 1590B. Four of them are DSPs and the fifth is an Atmel ATmega165 which controls the show. The DSPs are a single Wavefront AL3102 1KS and a trio of Wavefront AL3201B Digital Reverb Engines. A 16 position rotary switch selects the effect program in use and parameters are adjustable via four pots, a 3 position switch, plus an expression pedal input. An RGB LED indicates status. One true-bypass stompswitch handles signal chain switching for channel 1 and channel 2 is wired as always on (it's possible to do stereo, but the Lotus is really designed as a guitar input device with a line level effects loop). The interface to a host PC for programming is done via an opto-isolated serial port which may also be used to provide other things in the future.


Why am I telling you this?


Because I want you to be asking yourselves, "What would I do with 2 seconds of digital delay, 16 LFOs, and enough DSP horsepower to run over 220 2nd order parametric filters?"

Info on the chips is available at http://www.wavefrontsemi.com/

PCB layout for the prototype is almost done.

[doug deeper]

im thinking!
(this is going to be unreal!)
good work!

[ExpAnonColin]

:mrgreen:

[Arno van der Heijden]

Very cool!! So, where's the schematic ??!! :mrgreen: :mrgreen:

[squidsquad]

Mr. *low-tech* here w/a simple suggestion:  We've all heard the sounds runaway echoes make w/different EQs.  If there is a low pass filter....it degenerates to mud...using a high pass turns things into screechy static.
It would be nice to have a VERY gentle roll-off on both ends...so that a long delay...w/many repeats...would not turn into noise...but simply become *mid-rangey* and stay out of the way of new notes.  I'm an old Frippertronics Fan.  I suppose with them reverbs you get both a nice tight room sound and blend in a hall as well eh?  Sounds cool bro!

[MartyMart]

That sounds great Peter, can't wait for the next "installment"  !!

Marty.

[Andi]

That sounds very interesting indeed - and a pretty darned impressive achievement!

[Zero the hero]

CONGRATS!!!!
Looking forward to see it!

[Marcos - Munky]

Looks like a powerful machine. It was a very complicated build, I presume. Do you have a photo of the board of this "child" to show us?

[Jason Stout]

Cool! About how large is the board going to be?

[Mark Hammer]

I don't think we need to be "afraid" of digital anymore.  At the same time, for tinkerer-level DIY people, there is this particular challenge to meet head-on: http://diystompboxes.com/sboxforum/viewtopic.php?t=35168

[Peter Snowberg]

Thanks for the compliments.

Squidsquad: That's a great idea! Can I call that algorithm the Squidverb?? I'm a big Frippertronics fan too. Those two Fripp/Eno albums made a big impression on me.

I hope this device will allow people to get an idea like that, quickly prototype an algorithm based on modular functions, and to be able to tune the parameters in real time via a PC until they want to store it as a preset. The range of the pots and what they do is under programmer control.  

Here are a few more specs:

Total processing capacity: >144 MOPS (Million Operations Per Second); 133 MFLOPS (Million Floating Point Operations Per Second)
Real DSP Speed: >66.5 DSP MIPS
Controller speed: >11 RISC MIPS
Sample Rate: 48KHz
Sample width: 24 bits
Conversion style: Sigma-Delta
In/Out Channels: 2
Opamps: 5532 (3) & 34078 (1)
Coupling caps: Film
ADC: Wavefront AL1101
DAC: Wavefront AL1201
Control CPU: Atmel ATmega165 @ 12.288MHz
DSP1: Wavefront AL3102 1KS DSP
DSP2-4: Wavefront AL3201B Digital Reverb Engines
Flash: 512K x 8
E2PROM: 8K-32K x 8

Control A/D inputs: 5 (4 pots + 1 expression)
Control A/D resolution: 10 bits
Program selector: 16 position rotary switch
Control switch: 3 position toggle

Host interface: 5V serial via 1/8" stereo jack. (externally isolated)  
Expression input: 1/8" stereo jack
Input: Stereo 1/4" jack
Input Impedance: 47K/2.7M
Output: Stereo 1/4" jack
Output Impedance: LOW
Output short circuit protected: Yes. Indefinite length.

Power supply: 9-12VDC via 2.1mm coaxial jack (center minus)
Reverse polarity protection: Yes. Series Schottky Diode.

Board size: 2.2" x 3.65" (sized to fit into a 1590B or 1590N)

Construction: Mostly SMD SOIC & SMD 0603 packages. A couple are TSSOP and one is PQFP with 0.8mm pitch. All easily hand-solderable if you skip the triple cappuccino. I think it's actually much easier and faster to solder SOICs than DIPs. With tweezers, 0603s are very easy to solder too.

At some point I will offer some sound samples from the prototype and then start taking advance orders to cover 50 boards with solder masks, legend, and plated throughs. They'll probably be $10 each.

All my software for this thing will be all open-source and I would encourage other authors to make their creations open too, but there is capacity for somebody to create proprietary algorithms too. This is where everyone here comes in.

BTW: The effects loop is where you put the analog effects.

[moosapotamus]

Um... WOW! :shock:
Can't wait to check this out, Peter.

~ Charlie
(just slide a little food under my door occasionally, thanks)

[Paul Perry (Frostwave)]

With specs like that, I doubt it will be cleared for export! (just kidding.... I think!)
I'm not a programmer, but it has to be good to see the DIY field opening up to people who are into maths & DSP etc!!

[puretube]

over 12 hrs online, and nobody asked about tap-tempo yet... :?:  :?:  :?:

[scratch]

I'd be looking forward to a rackmount version w/ LCD ... Very Cool!!

Something else for your interest Peter that I stumbled on ...

http://www.elecdesign.com/Articles/Index.cfm?ArticleID=9876

[Peter Snowberg]

over 12 hrs online, and nobody asked about tap-tempo yet... :?:  :?:  :?:

LOL! :lol:

The really funny thing is that it won't do tap tempo without something external connected. There are plans for a "remote" with more buttons, knobs, and switches on it.

I guess a little programming and a switch that would send the expression input all the way to one extreme would do it too.... hmmmm....


Scratch,

Thanks for the link. There was somebody who came through here a few months back who was talking about building effects with those chips but I don't think I every heard more. That's pretty cool that they have a guitar phaser example! Those chips work using switched cap filters IIRC. I would love to hear how it sounds.

That is surely a company to watch. They quote 10,000 qty. pricing which is nice if you happen to be Roland. I'm guessing the low quantity price is 3 to 4 times the range they show. Cool chips.

[puretube]

xctly my thought (the switched xpr-input...)  :wink:

[tommy.genes]

Can you run VST plugins on this thing?

And it's in a 1590B did you say?

-- T. G. --

[Maneco]

Once again...congratulations!

Please add me to the mailing list to know when there are updates...i WILL build one (or more)

maneco@gmail.com

Thanks!