ChucK Guitar Workstation

Inventor

I'm setting up a guitar entertainment center based on ChucK. The photo below shows the very earlist beginnings of the setup. The computer is ten years old and the scope is probably from the 70's. Although giving up on electronics as a hobby, I feel compelled to just break out the guitar signal and put it on the scope. Who knows, maybe I'll get inspiration to do more with it. Anyway, just getting things set up and thought I'd share.

Guitar_Station1.jpg

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Just getting things in place...

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elektro80 · Posted: Fri Apr 25, 2008 2:09 am Post subject:

Cool!

Hey... what are your plans for ChucKing the guitar?

Are you going to build a ChucK app that can do Line 6 Pod style efx and amp models and such?

Kassen · Posted: Fri Apr 25, 2008 3:29 am Post subject:

Hey! What's in the arcade cabinet? You have a cab?!!! Can I be your friend?

Inventor · Posted: Fri Apr 25, 2008 6:48 am Post subject:

Kassen and elektro80, come on over and let's Rock! That's a genuine 1981 Ms. Pac Man machine, no quarters and plenty of classic arcade fun! I have it set up with the alternate mazes chip, which includes my favorite level which I call "Orange Velvet" cause that's what it looks like. Once I even made it through invisible level. Although invisible level appears fairly early on that chip, you get an extra feeling of Arcade-Godliness for completing any level that has "invisible" as it's main characteristic.

I plan to have similar Rock-Godliness moments jamming with my ChucK-enhanced guitar setup, elektro80. By now Kassen's read it three times over since I've been posting all over electro-music.com about the idea for a few weeks now, but if you haven't chanced across it in another post I'll explain.

I plan to do exactly as you suggest. Though not overly familiar with Line 6's goodies, the plan is to separate the strings and the identify the notes with software in ChucK's mind. Plus I'm setting up an accelerometer based motion sensor so that ChucK can know in real time the approximate XYZ position and spherical orientation of the guitar. Although I'm an inexperienced guitar novice, I plan to enhance the rock-like enjoyment of the guitar with my own custom software, and to make it be readily used by others to share the fun.

Already I've written an application that processes guitar audio that I created with my Guitar Lab software. It has a delay/feedback effect under mouse control, and I really enjoyed varying the effect in 2D using the mouse. It was way better than settings or even pots/sliders because of the dynamic effects that occur due to the transient nature of the control. It made crunchy, weird grinding noises mixed in with some feedback wailing and stuff like that. I'm sure 6 degrees of guitar motion tracking freedom will be even way more fun than that 2 degrees of freedom experience was!

I'll be posting on my progress to any relevant thread, so stay tuned to read about my guitar ChucKing adventure - and of course the source code will be free as always. ChucK Rocks!

Kassen · Posted: Fri Apr 25, 2008 8:08 am Post subject:

Cool! I like msPacMan a lot. I have the recent "plug joystick straight into TV" emulation, occasionally you still see msPacMan cabinets around here, mostly with Galaga in it as well. I like games like that in that they are hard but fair and you can play for short bursts. Most modern games are easy, unfair and you can't really enjoy them in short bursts.

Are you into more modern arcade stuff at all?

Inventor · Posted: Fri Apr 25, 2008 1:15 pm Post subject:

kijjaz · Posted: Fri Apr 25, 2008 4:39 pm Post subject:

ahhh a scope..
i wanna go analog also!
i've got some components from electronic stores...
it'd be nice to try making some crazy circuits. ^_^

(but not ChanalogucK)

Kassen · Posted: Fri Apr 25, 2008 11:51 pm Post subject:

Yeah, I used to play Quake too, HalfLife and Unreal too but at some point the genre stopped evolving (as I saw it) beyond having to buy ever more outrageous video cards so I quit.

I'm mainly into arcade games these days, especially 2d ones. I used to play 2s fighters (Street Fighter, Guilty Gear) but those only shine if you have friends that are into them as well, so I switched to shooters.

If you remember 1942 etc? Well, that style evolved since then and now you have stuff like Ikaruga;
http://www.youtube.com/watch?v=sd95jQ57_eM&feature=related
and Castle Shikigami;
http://www.youtube.com/watch?v=nXEHXeBmS-s&feature=related

Sadly Wikipedia merged most shooter articles and no longer is there a sepperate one on just the modern manic stuff;
http://en.wikipedia.org/wiki/Danmaku

I really like that kind of thing, even if I'm not even that good at them. It's also cool how quality releases of those let you turn your TV on it's side for the proper arcade experience. I also tend to like anything that's very weird and experimental (and mostly Japanese) then steal interface ideas to be used musically :¬)

I don't really have the space or the money to get into cabs which is probably a good thing because there's mame and I have a proper joystick with converter hooked up anyway.

Inventor · Posted: Sat Apr 26, 2008 12:15 am Post subject:

My favorite arcade games remain the classics, and I feel fortunate to have played many a Tempest game back in the 80's and then again in 1998 or so when I bought one and kept it for a few years. The whole story of how the game originated from a dream and took form at Atari is like a nostalgic engineering-themed fantasy or something. That, and I love the fast-paced gameplay. My high score was just over half a million back in the day.

Other favorites include Defender, Stargate, Galaga, Asteroids, Donkey Kong, Joust, and Qix. If you liked MAUI Pong, then maybe you would like to see the Pong Mechanik video:

http://www.youtube.com/watch?v=VsjoN7xWY5k

Getting back to the guitar topic, I've been thinking about tubes a little bit. I don't see a good way to simulate a tube amp in ChucK. I like the Dyno, and I'm thinking that it may be possible to chain many Dyno's together to create a tube amp profile. Each Dyno would have a different set point and slope, creating a somewhat smooth transfer function. I posted to ChucK Users list and Ge said that a tube amp Ugen was not in the plans so I'll need to create my own somehow if I want one. I think I'll code this up but just thought I'd mention it here first for comments.

Kassen · Posted: Sat Apr 26, 2008 12:52 am Post subject:

Why not roll your own compressor using a VCA, envelope follower and use a curve-table for the curve instead of chaining Dyno's?

Basically the whole trick is that you have a envelope follower that maps certain amplitudes at the input to certain amounts of amplification (particularly a amplification that's less then 1 when the input's RMS is over a certain amount). In between the two you can put any curve you'd like.

What about Metal Slug? Too modern?

Inventor · Posted: Sat Apr 26, 2008 4:27 am Post subject:

Kassen · Posted: Sat Apr 26, 2008 5:06 am Post subject:

Inventor · Posted: Sat Apr 26, 2008 6:08 am Post subject:

It could be implemented as a 3D shooter as well.

Attached is a start at a tube amp demo for testing some tube amp models. All it does now is a. no distortion and b. x squared distortion. I'm ramping a sinosc from 0V to 2V and sending it into a multiplier to create the x squared function a la kijjaz's technique. This way I don't need to sit and spin on 1::samp. Press "a" to hear undistorted sound and "b" to hear the x squared sound.

I can't seem to find any references on tube amp transfer functions, so I'm going to post somewhere about it.

Tube_Amp1.ck

Description:

Crude tube amp demonstration, doesn't do much yet...

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Tube_Amp1.ck

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Inventor · Posted: Mon Apr 28, 2008 3:58 am Post subject:

I have looked into tube models a bit. The simplest equation for a tube that I can find is: Iout = K(mu*Vin+Vout)^(3/2). Which produces transcendental equations (equations that cannot be easily solved without iterative methods). So I made the very crude approximation that Vout does not affect Iout much, which is not really true but it removes the transcendental term. Further, all the circuitry calculations concerning gain and output impedance and stuff like that do not matter to ChucK. We just need the general shape of the waveform from [-1, 1] to be modeled. So, the model is:

Vin => HPF @ 7 Hz => LPF @ 3kHz => x^(3/2) => dac;

In the attached model I left off the filters because they will have little effect at 220 Hz, and just swept the waveform into the x^(3/2) block. You press "a" to get the unmodified sound (whatever your computer does with a sine wave of gain 2), and "b" to get the tube model. Interestingly on this Mac, the response to "a" is warm and smooth, indicating some sort of tube model already in place for large amplitudes - I wonder what's going on there? Anyway, let me know how it sounds to you, thanks.

Tube_Amp2.ck

Description:

an oversimplified V^3/2 tube model

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Tube_Amp2.ck

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Inventor · Posted: Tue Apr 29, 2008 1:10 am Post subject:

That example from the previous post didn't work, this one does. I went over and over in my mind about how to do this properly and concluded that I should not solve the circuit equations, but rather put them into ChucK and let ChucK solve them. So ChucK does an iterative optimization to obtain the tube transfer function, neglecting capacitors and transformer, which it then outputs in a table.

I then paste that table into a pair of Gen7 Ugens in the other file for wave-shaping of the ramped sinusoidal test circuit. It's a good first working model of a tube amp! yay! I have learned so much in this little project, plus its also fulfilling to model a tube amp properly. Give it a listen and let me know what you think!

Tube_Eqn_Test3.ck

Description:

Solves the circuit equations for a tube preamp and outputs a table of simulation results.

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Tube_Eqn_Test3.ck

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Tube_Amp4.ck

Description:

Models a regular sinusoid and a tube amp, sounds "warm". Press "a" for sine, "b" for tube.

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Tube_Amp4.ck

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Inventor · Posted: Sat May 03, 2008 3:19 am Post subject:

I have a good one for you here. As posted in another thread but this time with source code. Tube FFT Warmer sweeps the decaying harmonics from zero to full amplitude three times at ten seconds each time in the output file. The result is a swept tube-like "warming" enhancement to the sound.

Tube_FFT_Warmer1.jpg

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The waveforms.

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Tube_FFT_Warmer2.ck

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The ChucK file that does this test effect.

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Tube_FFT_Warmer2.ck

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Tube_FFT_Warmer1.mp3

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The warmed up sinusoid sound file.

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Tube_FFT_Warmer1.mp3

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c-cam · Joined: May 02, 2008 Posts: 8 Location: ireland

That warmer sounds pretty phat inventor.

Inventor · Posted: Sun May 04, 2008 12:36 pm Post subject:

Inventor · Posted: Sat May 24, 2008 5:14 am Post subject:

Well, I bought the guitar now and a great amp to go with it, both Fender products but low-end ones. I also got a 1/4 inch plug and took a cut-in-half BNC cable that I had, and connected them together to create a 1/4 inch to BNC adapter cable.

This allowed me to plug the head phones out jack from the amp into my beat up old scope. Yay, real guitar waveforms! The image below is from a plucked E string (the bass, or lower E string). You can see that there is a strong harmonic content. At other times during the E-string note, the harmonics are greater than the fundamental, making for some tough note-detection work.

Anyway, now I have toys to play with, woohoo!!!

E_string_waveform.jpg

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Waveform of E string on my cheezy old scope

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Inventor · Posted: Sat May 24, 2008 6:43 am Post subject:

I couldn't afford a guitar tuner, but who needs one when you're a ChucK programmer? To tune my guitar I coded up the attached tuner. Just press a string number from 1 thru 6, then pluck the string. The tuner will isolate the desired open string frequency, then count zero crossings to calculate the actual string frequency. It then presents this information as a percentage value. So you keep adjusting the string until you reach within 1% of 100% and your guitar is tuned! Saved me at least fifty bucks and it's probably better than a commercial tuner too. You gotta lub that ChucK!!!

Guitar_Tuner2.ck

Description:

One ChucKtastic guitar tuner!

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Guitar_Tuner2.ck

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Inventor · Posted: Wed Jul 09, 2008 7:51 am Post subject:

I put together a web page that summarizes all of the technical details that were discussed here on electro-music.com regarding a Guitar Motion Sensor and posted them on my site. here is the url:

http://www.freedomodds.com/music/gms.html

Also I have an Ubuntu CD on the way finally. I ended up requesting a free one with 4 to 10 weeks delivery time. I have to be patient because I'm still paying off that car debt, but in the next few months things will clear up and I'll be able to buy hardware once again.

In the mean time I practice my guitar and learn some of the basics of how to play it. After all, when the time comes to demo the Guitar Motion Sensor, I'll need to actually *play* something on it for the video, won't I? So in a way the financial delays are a bit of a blessing in disguise, I suppose.