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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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Inventor
Stream Operator


Joined: Oct 13, 2007
Posts: 6221
Location: near Austin, Tx, USA
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PostPosted: Sun Jun 20, 2010 11:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

Jeff, to get more attack, just tap your output from the output pin of the summing amp. That is the way typical KS is done, but I enjoyed the sound better by tapping it from the filter output. Maybe both options should be made available on the third run of boards.

Les

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jeff-o



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PostPosted: Mon Jun 21, 2010 4:27 am    Post subject: Reply with quote  Mark this post and the followings unread

Inventor wrote:
Jeff, to get more attack, just tap your output from the output pin of the summing amp. That is the way typical KS is done, but I enjoyed the sound better by tapping it from the filter output. Maybe both options should be made available on the third run of boards.

Les


Cool, I'll give it a try.

And sure, that would be easy to do with a 3-pin header and a shunt, or with a dedicated switch.
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jeff-o



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PostPosted: Tue Jun 22, 2010 4:43 am    Post subject: Reply with quote  Mark this post and the followings unread

Well Les, I can see why you tapped the output where you did. When tapped at the output of the summing amp, the result does have a bit more attack, but it's rather harsh to my ears. Perhaps it's the stim source I'm using, I dunno.

Speaking of stim source, I did play around with that too. I tried sending my square wave pulse through a simple low-pass filter and it did help with the harshness, but killed the attack as well. So no big improvement there. Hmmm, would it help to rig up a more complicated stim source, like a white or pink noise generator? Or maybe a stim that has attack and decay characteristics of its own?

I also tried changing the low-pass filter inside the feedback loop, in an attempt to kill some of that high-pitched switching noise. I changed the 470pF cap to 0.01uF by soldering a 0.01uF cap across the terminals of the 470. It did seem to attenuate the switching noise a bit, but it also made the output sound muddy. Not an improvement.

I suppose my goal in all this is to get a bit more warm string sounds out of the circuit. Or at least, as much as this circuit (and the underlying algorithm) is capable of!
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Inventor
Stream Operator


Joined: Oct 13, 2007
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PostPosted: Tue Jun 22, 2010 9:43 am    Post subject: Reply with quote  Mark this post and the followings unread

Jeff, regarding the cap, 0.01uF is like way way bigger than 470pF, so yeah it would sound muddy. I'd try soldering a 470pF cap in parallel with the 470pF cap and see how that goes. Also note that the KS11 board has three loop filters actually. The main one is the VCF which is adjustable via the VCF pot and the VCF input. The other two are intended to attenuate the noise, and the caps on those can be made larger.

What I found in experimenting with ChucK software KS boards is that whatever you put into the stim input goes round and round in the loop and creates that kind of sound. So if you put a pulse of noise in you'll get somewhat of a noise-like sound out. If you put a sine wave burst in or a square wave or triangle wave burst into it, you'll be able to detect that in the output sound.

I'd recommend experimenting with different types of stim pulses to get the guitar-like effect you are looking for. I'd try noise first, yes for sure. The good news is that you've got approximately what you want, and the other good news is that now you're fine-tuning the sound - and that's music to my ears!

Les

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jeff-o



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PostPosted: Tue Jun 22, 2010 10:25 am    Post subject: Reply with quote  Mark this post and the followings unread

All good info! I chose the 0.01uF based solely on an RC filter calculation. I should have known better - I may be aiming for bass sounds, but high frequencies are still necessary or the output will lack definition.

I'll play around with the other filter caps a bit more to see if I can kill that noise. I want to see how low I can drive the BBD (and as a result, see how low I can get that bass!) I'm also looking into getting some (apparently very rare) MN3206 devices. 128 taps? Fun!

I'll also try feeding a pulse from an SN76477 into the stim input. What a neat chip. With the ability to control the attack, decay, duration and overall sound of the stim pulse, it's perfect for tweaking the sound. Perhaps it'll even make it into my final circuit!
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Inventor
Stream Operator


Joined: Oct 13, 2007
Posts: 6221
Location: near Austin, Tx, USA
Audio files: 267

PostPosted: Tue Jun 22, 2010 12:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yer on a roll Jeff, keep going! I ordered my Digikey parts for the KS11 board today, have many but missing some. Also must order Alpha pots from Futurlec. I like their prices but six weeks for delivery? man that sucks. Who else sells Alpha pots, 100kOhm, 0.2" pin spacing, right angle, short shaft - oh and knobs too?

Les

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jeff-o



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PostPosted: Tue Jun 22, 2010 1:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

Inventor wrote:
Yer on a roll Jeff, keep going! I ordered my Digikey parts for the KS11 board today, have many but missing some. Also must order Alpha pots from Futurlec. I like their prices but six weeks for delivery? man that sucks. Who else sells Alpha pots, 100kOhm, 0.2" pin spacing, right angle, short shaft - oh and knobs too?

Les


Well, you won't find anyplace cheaper than Futurlec, that's for sure. The ones I got from Digikey work, but you have to bend the pins a bit. I don't recommend them. You could try Mouser though, it seems they have a few Alpha pots. As for knobs, well, you certainly won't find them cheaper than at Futurlec!
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jeff-o



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PostPosted: Thu Jun 24, 2010 11:36 am    Post subject: Reply with quote  Mark this post and the followings unread

Well Folks, I went ahead and ordered four MN3206 BBDs. Normally I'd get more, but these were somewhat more expensive than the other MN320x series chips. They should arrive in, um, a few weeks I guess. If an MN3209 can get me down to 34Hz, can the MN3206 go down to 17? One can only hope!

I also started playing around with the SN76477 as a way of triggering the KS11. I ran into a bit of a roadblock when I realized the pins were spaced at 0.06" - it wouldn't fit into my breadboard! I've designed an adapter for it though, and hope to finish it off on the weekend so I can get with the noise makin.' My hope is that some combination of VCO, noise and envelope produced by the SN76477 will result in a sounds from the KS11 that are more string-like than what you can get with just a DC pulse or simple noise burst. I guess we'll see (or is that hear?)
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wmonk



Joined: Sep 15, 2008
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PostPosted: Thu Jun 24, 2010 11:42 am    Post subject: Reply with quote  Mark this post and the followings unread

Very Happy
I used the SN Voice (Thomas Henry module based on the SN76477) to do the same. The noise is nice, and gives an unique character. Have to say, the envelope isn't snappy enough. You really want a 'pulse' of a few ms, and this envelope doesn't do that very well. Hope the AR/AD envelope I'm working on now is a bit more snappy.

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jeff-o



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PostPosted: Thu Jun 24, 2010 11:55 am    Post subject: Reply with quote  Mark this post and the followings unread

wmonk wrote:
Very Happy
I used the SN Voice (Thomas Henry module based on the SN76477) to do the same. The noise is nice, and gives an unique character. Have to say, the envelope isn't snappy enough. You really want a 'pulse' of a few ms, and this envelope doesn't do that very well. Hope the AR/AD envelope I'm working on now is a bit more snappy.


Ah, I read a bit about the slow envelope on the various SN-voice pages. So even with the attack and decay times set to a minimum, how long of an envelope are we talking, here?

Not that it'll matter much to me in the end. I'll only have one SN chip in there running continuously, and I'll send stim pulses from it to the KS loops separately using individual triggers. At least, that's what I'd like to do. I'd like to avoid having one SN76477 per channel!
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jmejia



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PostPosted: Thu Jun 24, 2010 3:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

just sent payment for a board. i'm excited!

is anyone using this for general purpose delay or flanging? any opinions/results?

thanks!
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Inventor
Stream Operator


Joined: Oct 13, 2007
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Location: near Austin, Tx, USA
Audio files: 267

PostPosted: Thu Jun 24, 2010 11:02 pm    Post subject: Reply with quote  Mark this post and the followings unread

payment recieved, thanks. Will mail out boards next week.

I have run voice through KS before and it sounds like you are in a tunnel, so maybe that's like general purpose flanging. What you can do though is hook up a sequencer to the VCO and/or VCF inputs and create a modulated flanging effect.

Les

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PostPosted: Mon Jun 28, 2010 9:17 am    Post subject: Reply with quote  Mark this post and the followings unread

I'm playing around with the SN76477 now that I have my breadboard adapter built. I managed to get it to produce a continuous sound, but the "gunshot" example in the datasheet (the only example that uses the "one-shot" function) just doesn't seem to work for me. I'll play around with it more in the coming days to try to get it to do something fun.

As I mentioned before I'm not planning to use the SN's built-in one-shot to trigger the KS board (if indeed I end up using the SN at all!), so maybe I should concentrate on designing a neat little gate to control the stim signal generated by the SN chip instead...
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Stream Operator


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PostPosted: Tue Jun 29, 2010 3:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

Please see this thread:

http://electro-music.com/forum/post-300371.html#300371

for a new topic in which we discuss the availability of built Karplus Strong boards, thanks.

Les

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kkissinger



Joined: Mar 28, 2006
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PostPosted: Thu Jul 01, 2010 7:00 am    Post subject: Reply with quote  Mark this post and the followings unread

Inventor wrote:
To order KS boards, please send $15 each via paypal to lester.hall@comcast.net


Great! I just ordered a PCB. Where can I download the build docs?

This module will be a great addition to my synthesizer.

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Inventor
Stream Operator


Joined: Oct 13, 2007
Posts: 6221
Location: near Austin, Tx, USA
Audio files: 267

PostPosted: Thu Jul 01, 2010 9:03 am    Post subject: Reply with quote  Mark this post and the followings unread

Kevin, I can't wait to hear the great sounds you make on your ks board! I've got you down for one board. I've got 22 boards to mail out now, including the freebies, so I've got a weekend project now.

The latest docs are in the first post of this thread, which I have rewritten as a greeting and a place for the docs.

Les

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Inventor
Stream Operator


Joined: Oct 13, 2007
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Location: near Austin, Tx, USA
Audio files: 267

PostPosted: Thu Jul 01, 2010 11:34 am    Post subject: Reply with quote  Mark this post and the followings unread

Please see this page:

http://echuck.othomann.de/eChucK/eChucK.html

For the eChucK website that wmonk has kindly offered to host for me. It has KS info and documentation, so have a look.

Les

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Sound



Joined: Jun 06, 2006
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PostPosted: Fri Jul 02, 2010 8:30 am    Post subject: Reply with quote  Mark this post and the followings unread

Hello Inventor! The site looks very good!
I will be tuned for your next projects.
Sincerely congratulations, you are doing a great job. Very Happy
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Stream Operator


Joined: Oct 13, 2007
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Location: near Austin, Tx, USA
Audio files: 267

PostPosted: Fri Jul 02, 2010 8:55 am    Post subject: Reply with quote  Mark this post and the followings unread

Sound wrote:
Hello Inventor! The site looks very good!
I will be tuned for your next projects.
Sincerely congratulations, you are doing a great job. Very Happy


Thanks Sound, I'm using iWeb which came installed on my Mac mini. It's super easy to make good looking web pages with it. Just last night I added a KS documentation page as well, so enjoy!

Les

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Stream Operator


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Location: near Austin, Tx, USA
Audio files: 267

PostPosted: Thu Jul 08, 2010 10:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Well I finally got my ducks in a row and built a KS11 board. I attached it to a KS7 board and a breadboarded BS to make a "brick" of circuitry that makes great tunes. The KS11 generates sounds from the BS stimulus, and the KS7 acts as a resonator.

I love the deep bass of the MN3208 2048 chip, so i put that in the resonator, and I've tried all three chips (256, 1024, and 2048) in the KS11 board. Next I'll order some standoffs and small breadboards and wire up a nice BS that fits into the brick using a blank KS11 board to bolt it together. This will be my laptop battle performance music device.

I'll be featuring this thingie on tonight's Les Hall Show and probably on future shows, so be listen up if you are online.

Oh, and I've got all of the KS11 boards prepared in mailers, just have to fill our the international customs forms and go to the post office, which will happen within the next few days. So everybody expect your boards in a week or week and a half, paid ones and freebies too!

Les

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jeff-o



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PostPosted: Thu Jul 08, 2010 11:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Awesome. I won't be around for your show tonight, but I'm looking forward to hearing it once it's uploaded. My MN3207s and MN3208s came in the mail yesterday, so I'm itching to try them out, too!

I really must work on getting a nice stim source set up, though. I can use my iPod Touch to generate almost any stim I want, though I have yet to find an app that can generate "X" millisecond pulses for me. I'll need to rig up some hardware to do that, I guess. I'm looking at using a CD4098 for the job, since it requires fewer external components than a 555. Man, I wish I'd ordered a few of them in my last Digikey order! I got a talking-to from my wife because so many boxes have been arriving recently...
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Stream Operator


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PostPosted: Fri Jul 09, 2010 1:12 am    Post subject: Reply with quote  Mark this post and the followings unread

See this thread:

http://www.electro-music.com/forum/post-301336.html#301336

for a great show on KS.

Les

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Stream Operator


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Location: near Austin, Tx, USA
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PostPosted: Sun Jul 11, 2010 6:08 am    Post subject: Reply with quote  Mark this post and the followings unread

At this time I would like to discuss R27 and R32. These are the two current-setting resistors in the expo converter circuit outputs. The Thomas Henry Expo Converter pdf file that I have lists them at 27k Ohms for a 15V supply using a 3080 as the receive chip. So I guess if you are building for a 15V supply, 27k Ohms would be the value that you'd choose.

To get the 14.3k Ohms value, I scaled the value down to 9V, so that value is for running off of 9V batteries. Similarly we should calculate a scaled value for 12V supplies.

There are some other component tweaks to discuss, but this is the major one.

Les

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airlock



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PostPosted: Sun Jul 11, 2010 7:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Wow Les, you've created a little monster! Great job!
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Stream Operator


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PostPosted: Tue Jul 13, 2010 6:50 am    Post subject: Reply with quote  Mark this post and the followings unread

Airlock wrote:
Wow Les, you've created a little monster! Great job!


Thanks Airlock, yeah I think I'll start making them and selling them.

This morning, moments ago, I mailed out all of the boards. Please accept my apologies for delays. I'm a terrible procrastinator and doing "inside the box" things like filling out forms is not easy for me. Thankfully the post office folks were courteous, efficient, and helpful. Made a scary task easy. Whew! It's done! Expect your boards soon.

Les

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