The Karplus Strong eChucK DIY Project

[Jaba]

Hi Woody,
it would be great to have another run, thank you!

I would surely buy at least one PCB

Paolo

[dnode]

At last found the time to read through the whole thread, great stuff! Thanks, Les et al!

I would be mucho interested in five boards ... and willing to help out anyway I can!

Idea is to built up two for a module in, well, my modular ... and use three for a separate box incl. sequencer (of any kind?! BS?)

Please, shout if help is needed!

[Inventor]

dnode, i created "the brick"which was a bs into two ks boards, and it sounded awesome. into three would be something else. I strongly recommend your approach to use multiple ks together in each of the ways you choose to use the board as the sound so much better that way.

you might want different voices or you might chain them together for dronish weird sounds, lots of possibilities. I hope there is enough interest for another run.

Les

[de_engineered]

[de_engineered]

Is the stage count of the BBD essential btw? Sorry if this was answered somewhere in this thread - it is 22 pages long a this point !

Ie: is there a minimum for the effect to work, or might it be like reverb tanks with larger springs :: longer reverb times?

[Inventor]

[de_engineered]

[Inventor]

well, i would suggest prototyping any circuit geometry that you would like to create in software to see if it's what you think it is. Karplus Strong is powerful in it's simplicity, but physical modeling can be much more complex. Yes, you could parallel them for interesting effects. The KS board has a tap in it for inserting different filters and I'd suggest playing with that foremost.

Les

[mosc]

[mono-poly]

Totaly missed this one.
If anyone got a spare pcb, i'd be interested!

[Inventor]

Hi mono-poly, welcome to the KS thread, lol. I have recently learned that www.sparkfun.com has a circuit board service in which you can get just one board made or any number you want. They queue up people's boards onto a large panel, much like the MOSIS chip service that queues up people's chips to a wafer, then they have the panel cut up to individual boards for us. With this service there is no longer any need to get a large enough order together - we can just order the number of boards we want. Prices are always reasonable at Sparkfun too (If not darned low).

It's up to woody, but I would be in for four boards myself. Why don't we start a board run tally with this post. Please end your post something like this:

----------------------------------------------------------------------
Attention Woody Monk
Inventor: 4 boards requested
Running Total: 4 boards requested
----------------------------------------------------------------------

[elmegil]

I assume the service you're talking about is this one? http://batchpcb.com/forums.html/Products

[Inventor]

[elmegil]

I'm far too new to this to have ordered custom PCBs already . But it took me a bit to find the SparkFun link so I figured I'd post the direct link.

I'm still playing with small circuits...although most of my parts are here at this point, life has prevented anything very ambitious. Just a variant on the MFOS calibrator and a ridiculous variant on Ian Fritz's transistor matching circuit...and those are both really still in planning because I need additional 1% resistors for the first and sockets for the second. I'm building both on protoboard (though the demands of the Ian Fritz ckt are so minor that I could practically wire it into the lid itself instead).

When I say ridiculous...I ordered a 4PDT on-off-on switch to switch between NPN and PNP variants with one circuit...without paying close attention to dimensions...and the switch I got was HUGE. It fits in the planned project box, but it's going to look very silly. Luckily the switch for transposing the emitters is from the same series/mfr, so they'll look silly together.

[Inventor]

elmegil, nice to read your sharing of your project experiences. Those of us who have been around longer get a kick out of beginners' stories because they remind us of our own beginnings, both the success and the failures. The giant switch is a learning experience, and thanks for the link.

Les

[elmegil]

I posted the unwired but mounted picture here: http://electro-music.com/forum/topic-51990.html Hopefully I'll get a chance to wire it up tomorrow, at which point I'll take some more pix and post to the build thread.

[e-grad]

I’m stuck with my project. Could someone please tell me whether I got the following right:

Some panels for this project include a ‘resonance pot’ and a ‘trigger level’ pot:

R43 of the summing amp is „resonance pot“?

Trigger level = a pot not shown on the schematics which is wired in front of “X4/Stim”?

There are three pads right above U3. Does a 100nF (= 0.1µF) goes here leaving the middle pad unused?

I received in a trade two different Les Hall’s Karplus Strong boards. One is from 2010 which is discussed in this thread. The second one is from 2009. Is there any documentation for this board available?

Any hint is highly appreciated!

[CreatorLes]

Hello to anyone who ever had or ever will have a Karplus Strong board developed by us in this thread. I have decided to revisit this project, doing another production run!

I'm not exactly sure precisely what this will entail as my goal is to remake "The Brick" music synthesizer. I suggest if you are interested in this project that you review the audio sales demo of the brick that I posted here:

http://electro-music.com/forum/phpbb-files/the_brick_demo_20110118_10084_203.mp3

I would like to best serve the community by offering new boards to anyone who had troubles or didn't complete their project in the past as a free service, including helpful support here in this thread at electro-music.com.

As I am not wealthy, I will be taking preorders for this project. I will offer the boards at a slightly higher price than before so as to accommodate the free boards for people who will receive them and also a small donation to electro-music.com.

I'm not sure what else to say at this point, other than I'm open to suggestions as to what to do. Do we want another modular board that can also be fit into "The Brick" format, or how about we avoid the circuit board and use Adafruit's PermaProtoBoards with very specific parts installation instructions? I could see us going that route and avoiding a custom circuit board altogether.

Let's discuss this.

Les

[CreatorLes]

My plan is the following. Take a look at the image attached to this post. It shows the top and bottom of a half-sized perma-proto board from Adafruit, plus a half-sized breadboard. The boards are available in full, half, and quarter size.

I figure if we place two breadbords side by side and join them, they should ideally hold a neatly laid out version of a Karplus Strong board. By using my Neat Freak Technique to wire up the boards (which is easy to learn but requires some small amount of patience), they will be neat and clean in appearance and functionality.

I will do a design and publish exactly how many wires of what length are required and where they go. Then it is a simple matter to translate the circuit to the perma-proto boards or to construct a duplicate (recommended).

In this way the community is free to develop mods and options together and some or perhaps all of the mods can be integrated into the design. We can evolve the design to a modern form, revising and improving it, then go for another board run.

Speaking of which, I can begin doing some research tonight into parts and such for this. I have a $100 gift card coming my way, and I have one full length breadboard and some full length perma-proto boards. I could get to it right now, which I think I will!

Les

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Perma-Proto Half-Sized Breadbord PCB pack $12.50.jpg
Description:	Perma-proto Pack for $12.50 sold by www.adafruit.com - illustration shows top and bottom and breadboard equivalent of half-sized board. Full and Quarter size also available.
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[elmegil]

[CreatorLes]

[CreatorLes]

Sigh - I tried about six or eight times to make a video on the Neat Freak Technique but they all turned out poorly. I'm going to ask my friend who is a filmmaker to help me.

Les

[CreatorLes]

In the chatroom tonight I had some discussions with debterminer, who has agreed to do testing for this project and to kit parts. I really appreciate that because I don't do things like kitting very well. So you'll be able to buy kits from us.

That's a really good thing because I've decided to make this a digital design based on building blocks of the humble yet powerful ATtiny series of microprocessors, specifically the ATtiny85 and possibly the ATtiny84 if need be. The 84 is just an 85 with 14 pins instead of 8 pins on the package. That means the 84 offers way more I/O if we need it for a particular function.

For example, we will need a CV input. This can be accomplished with an ATtiny85 reading the CV with it's ADC and sending out a frequency with the tone() function. In this way we can get whatever usable bits of the ten-bit ADC into the fray and cover a wide range of octaves, and it won't require expensive circuitry. We can even put a cal input for tuning the device according to your 5% or 1% components.

Then there can be other functions such as variable delay line of up to 256 steps per module (or more as the device has a 0.5K byte SRAM. The program storage is even more generous for a $2 microprocessor part, so lookup tables and the like are possible. For analog output, both successive approximation DACs (delta modulators) and R2R ladder circuits are possible as well as n-bit inverting opamp stages. We can offer all three types to choose depending on requirements or preferences.

My plan is to make a rockin' synth based on CV, or a couple of types of sequencers plus variable delay lines in feedback. I'll also offer exacting breadboard and perma-proto board layout instructions and maybe even have some PCBs made if there is enough interest.

Once that project is complete, the pre-programmed ATtiny85 and ATtiny84 chips can be made available for your purchase individually or in packs to build whatever circuits you like.

All the designs will be open sourced and made available for free so that you can program your own chips, modify the code, and even create your own designs for sale by yourself or by us.

Sounds good huh? I better get to designing! see ya!

Les

[CreatorLes]

Today I made a CV2F chip design. It's just a chip, no external components and you put a pot on it or a CV into it at 1V to 5V, out you get a freq that varies over 5 octaves.

Planned are example circuits with input protection and upgrades to the chip so it can be configured to various CV mappings, stepped or linear, stuff like that. Good thing Jason and I decided on the ATtiny84 instead of the ATtiny85 chip. the 84 has way more pins extra for configuration.

I met with my friend Ly (pronounce Lee) today and he want to use the modules to make a synth that I will help him create. We had a good exchange and talked lots of ideas for the synth. Ly gave me handwritten list of all the modules we should eventually get around to making and I plan to get into them all in time. Plus all kinds of crazy ones like bittwister and digital mayhem and whatever.

But what I think the best demo of this will be to make a brick, that's two KS modules, with CV and Pots driven by a kbd and/or guitar. Imagine playing a thing that makes sounds like this:

http://electro-music.com/forum/phpbb-files/the_brick_demo_20110118_10084_203.mp3

Les

[aerogramma]