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 Forum index » DIY Hardware and Software » Les Hall's Projects including eChucK
The Karplus Strong eChucK DIY Project
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jeff-o



Joined: Jul 19, 2009
Posts: 97
Location: Ontario, Canada

PostPosted: Mon Nov 09, 2009 4:51 am    Post subject: Reply with quote  Mark this post and the followings unread

Sounds like progress to me! I've bookmarked that page, I think it will be very valuable in the future, thanks!
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Stream Operator


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PostPosted: Sat Nov 14, 2009 12:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

Time for a progress report. I cleaned up and rearranged my computer desk so that now it is also an electronics workbench as shown in the photo below. This means that I can listen to music and chat and surf the forum like I enjoy doing, and also easily mix in some prototyping. Before I had to go to another desk to work on the prototype so I just rarely got around to it. The result: progress.

I changed the cap on the VCO to 18pF to increase the frequency, then changed the feedback resistor to 60.4K (the values are approximate and can be mucked with if desired). Then when I built the level shifter I changed the base resistor to 20k Ohms. It works fine.

Just now I completed wiring up the delay line and tested it by sending in a potentiometer adjustable DC signal. It works great. It tracks the input properly and the switching noise is about 50mV pk-pk. That's without any filtering.

I just love it when things work out properly. Next I'll wire up the VCF. I'll keep you posted.

Les


KSProto.jpg
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My new workbench wit KS Proto under test
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KSProto.jpg



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Stream Operator


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PostPosted: Sun Nov 15, 2009 10:49 am    Post subject: Reply with quote  Mark this post and the followings unread

I have good news! Today I woke up at 3am or so and worked for 8 hours on the KS proto. Now it works! In fact, it sounds so good that we're going to do a fun little radio show on radio.electro-music.com featuring a demonstration and explanation of the circuit. We haven't set a day or time yet, so stay tuned!

Les

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Dan Lavin



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PostPosted: Sun Nov 15, 2009 6:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

Les,

This is great news! So you actually sleep?! I would've bet against it.Wink
No, seriously, I'm pumped! I'm really looking forward to this.

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PostPosted: Sun Nov 15, 2009 6:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

Dan Lavin wrote:
Les,

This is great news! So you actually sleep?! I would've bet against it.Wink
No, seriously, I'm pumped! I'm really looking forward to this.


Dan, I usually sleep in naps due to my schizophrenia. I am often on edge, waking up in fear of someone being in my apartment... Sad But it does allow me to get a lot of work done.

The show will be this Tuesday (It's Sunday evening right now, so in two days) at 22:00 GMT which is 5:00pm EST (my time) and 2:00pm PST. It will be one hour long and I will interact with people in the chatroom while playing around with the prototype and discussing the circuit.

After that I'll Order a parts kit, finalize the circuit board design, and have some boards made. I will keep at least one board and sell the rest at a modest mark-up. So boards are on the horizon - whoot!

Les

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DGTom



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PostPosted: Sun Nov 15, 2009 9:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

Love the sleek new set-up Les! I should take a page from your book & replace the ever growing pile of papers, books & debris that surround my computer with a bench supply & proto set-up Very Happy
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PostPosted: Mon Nov 16, 2009 9:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

Now that the design is working, I have updated the schematic with all of the changes and done a new PCB placement with autoroute, both shown below. There were 10 changes including both circuit and component value refinements. The only thing left untested are the CV inputs.

On the PCB, note the way cool guitar logo that wmonk made for the project. Thanks for that, wmonk!

Please review these images and critique them if you feel so inclined. I've decided to save Rob and Scott's suggestions for future versions of the board, since there seems to be a good amount of interest among our DIY brethren / sisterhood for this board and also because the prototype works so well.

Next I will order one kit of parts from DigiKey and SmallBear so I can check footprints and spacing and such things before finalizing the design and having boards made by E-TekNet.

If you would like to be the first one on your block (or in your country for that matter) to have a working analog Karplus Strong unit in your modular, please post to this thread so I have an idea of how many boards to order. Obviously since the NRE charge is fixed and non-trivial, the more first run orders we get, the cheaper each board will be.

I just got done selling some little PCBs at a 10% markup and to be honest, I lost money with all the incidental expenses like choosing priority mail instead of cheaper shipping methods, gas, parking, etc. Therefore I would like to price the boards somewhere in the neighborhood of cost plus 50% plus shipping. In fact, that's going to be my new markup for anything I create and people seem to think that's a fair markup, especially when you consider the umpteen hours that have gone into this project. If you feel that is too much, please let me know.

Enjoy,

Les


KS3SCH1.jpg
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Karplus Strong Rev 3 Schematic
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KS3SCH1.jpg



KS3PCB1.jpg
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Karplus Strong Rev 3 Printed Circuit Board
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KS3PCB1.jpg



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electri-fire



Joined: Jul 26, 2006
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PostPosted: Tue Nov 17, 2009 4:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Inventor wrote:
If you would like to be the first one on your block (or in your country for that matter) to have a working analog Karplus Strong unit in your modular, please post to this thread so I have an idea of how many boards to order.

I want to be the first on my block, so I'll have one. On a national scale I suspect I'll have to share the honor with Wmonk?

Inventor wrote:
I would like to price the boards somewhere in the neighborhood of cost plus 50% plus shipping.


That's ok Les. Actually I feel kind of bad you lost money on the Lunetta boards. So go check your Paypal my friend, I've made a downpayment to facilitate future developements. Knowing you, I'm sure these will come.

.
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PostPosted: Tue Nov 17, 2009 5:02 am    Post subject: Reply with quote  Mark this post and the followings unread

electri-fire wrote:
Inventor wrote:
If you would like to be the first one on your block (or in your country for that matter) to have a working analog Karplus Strong unit in your modular, please post to this thread so I have an idea of how many boards to order.

I want to be the first on my block, so I'll have one. On a national scale I suspect I'll have to share the honor with Wmonk?


Yes, Mathe, I cannot speak for him, but wmonk seems to really like this design so I hope to include him in the first run of boards. Thank you for ordering one of them, I hope you like it!

electri-fire wrote:
Inventor wrote:
I would like to price the boards somewhere in the neighborhood of cost plus 50% plus shipping.


That's ok Les. Actually I feel kind of bad you lost money on the Lunetta boards. So go check your Paypal my friend, I've made a downpayment to facilitate future developements. Knowing you, I'm sure these will come.

.


Why thanks again! That was a nice healthy advance and it will really help grease the wheels of my projects!

Les

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wmonk



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PostPosted: Tue Nov 17, 2009 5:09 am    Post subject: Reply with quote  Mark this post and the followings unread

electri-fire wrote:

That's ok Les. Actually I feel kind of bad you lost money on the Lunetta boards. .

Me too.

Did you test the 1V/Oct tuning of the board Les? Can be easily done with a battery, a SPDT switch and a few resistors (or a little trimpot).
First apply 0V, and then 1V, and adjust thing until it works ok. After that, try it with 1V to 2V, to check if things are still ok.


Inventor wrote:
Please review these images and critique them if you feel so inclined. I've decided to save Rob and Scott's suggestions for future versions of the board, since there seems to be a good amount of interest among our DIY brethren / sisterhood for this board and also because the prototype works so well.

Perhaps it's possible to get it a little more compact, so they are cheaper and smaller?

electri-fire wrote:
I want to be the first on my block, so I'll have one. On a national scale I suspect I'll have to share the honor with Wmonk?

Ha! We're the first! Yoohooo! Tried to send a small package to the States yesterday, and it's way more expensive to send packages to the States, then to send packages from the US to the Netherlands.
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PostPosted: Tue Nov 17, 2009 10:34 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey wmonk, some thoughts here. First, thanks for your sentiment but it's OK that I lost money on the eChucK Lunetta breakout boards. That's because of two reasons. First, I am just testing the waters and figuring out how to make selling prototypes and products practical for everyone including myself so I expect some errors at first. Second, evan at a loss there was considerable help in paying for this batch of boards. I have no need for 100 of them just yet, so even at a loss it helped out quite a bit. So no worries. I've learned from experience and next we'll try out a 50% markup as I mentioned, which seems fair enough to everyone involved.

As to testing the CV inputs, yes I'd better do that before committing to a batch of boards. I will do that after the show this afternoon because I don't want to disturb the prototype until the show is over. The inputs, however are linear not exponential. I plan to make the next revision of the board be exponential.

As to board size, there is a reason I made the board so big. In addition to it's use as a modular synthsizer product, the board can also be used to make an eChucK "brick", or stack of boards that performs one voice of a song. For them to stack properly, they must be the same size and have holes that align. The Boolean Sequencer board is much more densely packed and the clock / timer / battery board need to be big enough to hold two 9V batteries plus circuitry. So the Karplus Strong board is not fully condensed down to it's minimum size for that reason. The size of board that I chose is the maximum size of free EAGLE CAD and low-cost EAGLE CAD, so that was the reason I chose that exact size.

Thanks for your interest in my projects, wmonk!

Les

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PostPosted: Tue Nov 17, 2009 12:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

I have not found someone to do the kitting for this project, so I thought about it and decided to do the kitting myself. I don't know what the kit cost is yet but I will price it the same way as the boards (cost + 50% + shipping). Naturally, it will be cheaper if you order the parts yourself so it's up to you. I will post a bill of materials when I actually have one prepared. To gauge interest, post a message to this thread if you'd like a kit in addition to a board.

I should also mention that since these are first-run boards, the people who order them will be somewhat a bit of experimenters themselves. That's because the component values have some room for experimentation, which is a good thing because we can customize the boards for specific requirements. For example, we can adjust the VCF capacitor up if you prefer a wider range of bass guitar sounds, etc. So if you order a first-run board, be prepared for the opportunity to tweak the module to your specific requirements.

Les

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Dan Lavin



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PostPosted: Tue Nov 17, 2009 2:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

Les, I'll be up for the boards as they each become available. I'll source my own parts, thanks anyway!
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wmonk



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PostPosted: Tue Nov 17, 2009 4:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

Some ideas to get on the final board (not this proto board) besides the expo converter which makes it very useful with sequencers and modulars.

I think it's nice to set the pot spacing to one of the modular formats.
Don't know the spacing for Synth.com, but I think it's the same as MOTM: 1.625"
For Serge like systems, and I think Frac too, it's 1"

Thomas White did the spacing on his LPG pcb in MOTM format. One of the interesting things of his pcb is the extra holes for different kinds of potentiometers. A picture says more, so I refer to his build documents: http://www.naturalrhythmmusic.com/lopass.html

Most modular output levels are 10V pk-pk. How is the output level of this board?
Perhaps a nice future thing: a little VCA with guitar amp characteristics like a possible (little) distortion? Wink
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DGTom



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PostPosted: Tue Nov 17, 2009 5:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Very Happy

Just echo my previous excitement here! Put me down for at least 4 boards; altho this talk of value tweaking has me salivating as I imagine a panel laid out according to voices.

Perhaps 3 options for kits would help; Just board, Board + ICs, Full Kit. This would mean you don't have to have a huge stash of resistors / caps etc. Plus make it appealing right across the spectrum.

I'm keen to know the pk-pk swing as well, altho, would this depend on the rail voltages wouldn't it? I don't mind adding a little make-up gain amp, or even a 4069 fuzz cct. alongside Cool

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PostPosted: Tue Nov 17, 2009 6:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

I like all of the above suggestions, wmonk and DGTom. I will add gain to the output buffer of this board so that the levels are +/- 10V. I will also space the pots 1" apart and make a multiple footprint for them. I'll see if I can also do 1.65", unless you prefer 1.65" over 1" - choose for me please (which is most popular, I dunno). wmonk, do you have any particular pots that you would like footprinted? Pleas provide me with DigiKey part numbers and I will make the footprints accordingly.

Regarding the spacing of the pots, is there any positioning vertically that you would like? Squoosh them to the top, bottom, or middle?

DGTom, I will create custom kits with any desired combination of parts for the first-run boards. Once the design stabilizes and becomes an electro-music store product, it's up to Howard whether he wants to stock chip-only kits. I will provide whatever DIY hobbyists request within reason.

Also DGTom, would you like four of these now or just one and three from the next batch? I ask that because there will almost certainly be board changes discovered in the process, so you might want to just get one now and more later. I'll order however many you want though.

Expo converters and distortion amps? sure, why not? hmmm, maybe I can add distortion to this board and just not populate it if you don't want it. We'll see.

Thanks for the suggestions and the orders guys, you are champs!

Les

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DGTom



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PostPosted: Tue Nov 17, 2009 6:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ah good call! Just one for the purposes of exploration would be great, I'm sure between all of us we'll discover all kinds of ways of making the next batch better & better Very Happy

I think on board expo. would be great for trad. sequencing, distortion should be left up to the end user I think, I'm sure we all have our own, very specific, tastes when it comes down to that - a solid, flexiable core would provide us with the optimum starting point.
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Dan Lavin



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PostPosted: Tue Nov 17, 2009 7:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

Les,

Sorry I missed your show tonight. Are you able to post an samples for those of us that missed it? I'm kinda curious how this thing sounds. Thanks!

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PostPosted: Tue Nov 17, 2009 7:35 pm    Post subject: Reply with quote  Mark this post and the followings unread

Dan Lavin wrote:
Les,

Sorry I missed your show tonight. Are you able to post an samples for those of us that missed it? I'm kinda curious how this thing sounds. Thanks!


Dan, I recorded the show and I'm reviewing it right now. I'll post it to the streaming radio forum when I've listened to it, so check for it in a couple of hours.

Les

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rubendelacosta



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PostPosted: Wed Nov 18, 2009 9:38 am    Post subject: Reply with quote  Mark this post and the followings unread

just listened to your radio show and i really enjoyed the the karplus strong!
i'll be up for at least one board

congratulations on this project
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yerpa58



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PostPosted: Wed Nov 18, 2009 12:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

Inventor,

That K-S schematic is a very interesting and unique looking design. For those of us who missed the radio show, is there a way to hear some samples? Keep up the good work!
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Blue Hell
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PostPosted: Wed Nov 18, 2009 1:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

yerpa58 wrote:
For those of us who missed the radio show, is there a way to hear some samples?


Les posted a recording here.

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DGTom



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PostPosted: Wed Nov 18, 2009 5:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

Got half-way thru the show yesterday before being interupted, will be getting thru the rest in a moment.

AMAZING sounds! I did Laughing at the motercycle sounds, but my jaw dropped several times when you were dialling around the low freq. bass & guitar-ish tones & the percussion sounds! Wow! amazing! Can't wait to get my greasy mits on this gem Razz
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PostPosted: Wed Nov 18, 2009 6:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hahhahha, Thomas, glad you like it. We can thank the creators, Karplus and Strong for that.

wmonk showed me how to make PDF's from EAGLE CAD, so now you can read all the details without having to squint at illegible screenshots. Here is the current schematic, pun intended...

Les


KS4.pdf
 Description:
Karplus Strong schematic, now actually readable...

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Blue Hell
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PostPosted: Wed Nov 18, 2009 6:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hey a readable one thumleft
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