The Karplus Strong eChucK DIY Project

Inventor · Posted: Mon Aug 24, 2009 2:46 am Post subject:

Here is a photo of the mysterious chopsticks. It is a proto board with a notch cut out of it and when seen from that angle it looks like chopsticks. Sorry photo is blurry.

Actually I'm surprised that you guys were distracted by the chopsticks so much that you missed the reflection of the UFO in the background! Laughing

chopsticks.jpg

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The mysterious chopsticks

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Inventor · Posted: Mon Aug 24, 2009 4:19 am Post subject:

As a sort of test-fit, I did a board placement this morning, shown below. While the BS part of the BSG fits nicely, there is little room left for the G part (KS). So what I'm thinking of doing is simplifying the LEDIL logic somehow. I'll let you know how that goes.

Les

BSG_board1.jpg

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bsg board layout

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Inventor · Posted: Mon Aug 24, 2009 5:15 am Post subject:

I simplified the LEDIL to make more room on the board, and now there is plenty of space. You can see two sections of LEDIL in the attached schematic. There are no series resistors with the LEDs and no transistor buffer stages either. I may have to adjust the bias and gain of the output, but at least I think the output will be correct.

The performance difference here is that the input LEDs will get dimmer when there are more of them on at the same time, but that saves on battery life and makes for a more interesting display perhaps, so it's not really a negative.

BSG_schematic2.jpg

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LEDIL Schematic, simplified

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droffset · Posted: Mon Aug 24, 2009 4:59 pm Post subject:

Looking great, you're really cranking on this , go, go, go, go.

Inventor · Posted: Mon Aug 24, 2009 9:56 pm Post subject:

Ty droffset, i need motivation like that. Shown is a layout with simplified LEDIL and two opamp chips on the output. Should be enough room for a KS circuit, should I ever get to testing that. Bet I should huh? Anyways ty and best wishes droffset.

Les

BSG_board2.jpg

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getting there

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Inventor · Posted: Tue Aug 25, 2009 3:29 pm Post subject:

OK folks, I'm ready for a design review. The attached files are the schematic and board files for the BSG board, or BSKS as I've been calling it. I'd appreciate if anyone could review them and let me know what you think.

Thanks,

Les

BSKS4.sch

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Schematic

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BSKS4.sch

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BSKS4.brd

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Board

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BSKS4.brd

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Dan Lavin · Posted: Wed Aug 26, 2009 5:49 am Post subject:

Les,

these are Eagle files? Just checking.

regards, Dan

Inventor · Posted: Wed Aug 26, 2009 5:54 am Post subject:

toad008 · Joined: Sep 01, 2007 Posts: 30 Location: maryland/usa

dude i like the pictures! Smile

Where do i apply to be your lab studio slave? haha serious ... droooollllll

Toadie Shocked

Dan Lavin · Posted: Wed Aug 26, 2009 7:15 pm Post subject:

Les,

If you can wait until the weekend, I'll see what I can do to review. Too many pushy customers are driving me crazy right now. State Machine can vouch for my pcb work.

regards, Dan

mosc · Posted: Wed Aug 26, 2009 9:20 pm Post subject:

On your boolean sequencer, what effect would using binary counters instead of decimal counters?

Inventor · Posted: Thu Aug 27, 2009 10:10 am Post subject:

antman, sure I'm happy to wait for the weekend, I'm a little burned out after all that work.

Howard, This thing needs a binary counter, yes. I changed the counter from a 4017 decade counter to a 4040 binary counter for just that reason, it's what I need for the job. I had misunderstood and thought that a 4017 was a 10-bit binary counter, but now that I've seen it used in the baby 10, I realize my mistake.

To all, some issues I am concerned with are: will the new LEDIL really work? I have just thought it out and not constructed it. Also will the Karplus-Strong circuit work with this very simple implementation? I'm concerned about the HF pulsed input burst not doing the job and also the AC and DC bias are tied together. Maybe we can work out these details somehow and make this thing the DIY project it really should be!

Les

Inventor · Posted: Thu Aug 27, 2009 10:11 am Post subject: Re: yo inventor

mosc · Posted: Thu Aug 27, 2009 5:32 pm Post subject:

I usually drive LEDs with a buffer chip of some sort. It looks like your circuit can present some very large and quite variable loads on the counter. It's been a while since I worked with CMOS, but if I remember correctly, most logic devices aren't designed to drive loads. They look to drive very hi Z lines.

Inventor · Posted: Thu Aug 27, 2009 7:35 pm Post subject:

wmonk · Posted: Fri Aug 28, 2009 3:57 am Post subject:

Isn't panel mounting the LEDs and switches an option? You save a lot of space on the PCB if you do so. Or make 2 PCBs, one for the LEDs and switches, and one for the other parts, en connect them with a few ribbon cables.

Inventor · Posted: Fri Aug 28, 2009 4:47 am Post subject:

Inventor · Posted: Sat Aug 29, 2009 1:20 am Post subject:

Actually, another option is to do separate Boolean Sequencer and Karplus-Strong boards. This alternative makes some sense because modular synthesis folks might want to make only a K-S or only a BS board for panel mounting.

Certainly a K-S board does not seem to exist and with a whole board for K-S, we could have lots of features like pseudo-random noise burst and other input styles, filter options, etc. Besides, I do like the idea of an extended board pair for the stand-alone version rather than a sandwich board pair.

Just tossing ideas around. Clearly the board needs major revisions and I'm looking forward to reading more design review comments.

Les

Inventor · Posted: Sat Aug 29, 2009 2:23 am Post subject:

Also, another thing I'm not too hot about with the LEDIL is that it shows inverted bits. You see blinky lights according to your switch selections, but the lights are "on" when the logic is "off", so you only get a note when nothing blinks. This is counter-intuitive, though it still makes for a nice light show.

I'd prefer to just do it with standard LED outputs on resistors, and with a dual board approach that would work.

Les

droffset · Posted: Sat Aug 29, 2009 2:56 am Post subject:

Is the 4049 hex inverting buffer useful here?

wmonk · Posted: Sat Aug 29, 2009 3:43 am Post subject:

Uncle Krunkus · Posted: Sat Aug 29, 2009 4:51 am Post subject:

Jesus H Christ Les!!@!
Are you criminially insane or what?!?! Laughing

Love your work dude.
It's gonna be a week or two before I work out what the hell is goin on here!!

Inventor · Posted: Sun Aug 30, 2009 2:50 am Post subject:

Thanks wmonk, that's just the LED bargraph part I've been looking for!

I also like the notion of a separate KS board, and with a filter option - whoot! This will go into the plans for sue!

Les

JovianPyx · Posted: Sun Aug 30, 2009 3:21 pm Post subject:

How many strings will the KS board support? Is it polyphonic?

Inventor · Posted: Sun Aug 30, 2009 4:57 pm Post subject: