Instructables
Picture of The Prism: A Laser Synth-Guitar
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The Prism is, quite simply, the best laser guitar on the Internet. At least I think so. I hope that you take these instructions and not only make your own, but improve on my design!

I suppose I should clarify what the Prism is: It's a bit like a guitar with some synthesizer mashed in. It has aspects of a theremin and a laser harp thrown in to boot. In short, it's not like anything else, and you can use it to make some really neat sounds. Anything from cold Sine and harsh square waves to heavily distorted noise.

At its heart the Prism features a VCO (Voltage Controlled Oscillator), based around the very shiny XR2206 monolithic function generator. The octave range is selected by blocking one of four laser "strings," and the pitch is controlled by the position of the musician's hand on the fretboard. The musician has the option of selecting a sine, triangle or square wave. The sine and triangle waves can be skewed using a separate Skew control.

It also has two other controllable oscillators, one acting as an LFO (Low Frequency Oscillator) and the other acting as a Sync generator.

I designed the Prism to plug into any regular guitar amp, with no computer required. In fact, there is no programming involved at all in this project! It is just as portable as a regular guitar, and meant to be used at gigs or wherever else an "alternative" instrument is needed!

Here is a video showing the basic functions:



And here I demonstrate the on-board effects:



Visit the Sample page to hear me "jam!"
 
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Darfka7 months ago

I think this is a truly great project, but one very bad thing about it, it's that it seem very hard to "pluck" the cord you want to without playing the other. It's not instinctive at all. I'm thinking about making one, but first, I have to resolve this issue because, if I don't, it sure this instrument will end in a box somewhere.

lukeggg8 months ago
This is a great project and I am currently working on a similar one myself. I see that you have actually made some serious improvements to this guitar in this youtube video http://www.youtube.com/watch?v=4CnRsTaShUU

I have watched the above video a bunch of times but I can't figure out what kind of sensor you are using to detect which fret you are on, and how it is precise enough to get the 'bending' within the fret. I see four sensors where you currently have the one on the old prism guitar, but it seems much more sensitive than just four IR sensors.

My last question is about how the actual guitar sounds, where it is clearly no longer a sine wave/triangle wave/etc. Did you just program each 'note' to an audio file which would play when triggered? Again, great project and I look forward to hearing how you changed the prism guitar.
synthdust1 year ago
Very awesome. How are you using the neck to control the pitch? john_a4321 kinda asked the same thing. The way you described it, the range finders control the pitch, however when I watch the video if you playing, it looks like the range finder is just used to "pluck" the "string" and you are using the neck in a more traditional way to actually get different notes out of the string. What is going on here?
john_a43211 year ago
what is the sensor of the neck of the guitar
akinich2 years ago
hey........its been along time since ive seen this instructable
im still fascinated with it...
just to make it simpiler can you remove most of the stuff and put in an arduino?
tejask2 years ago
can i gt the schmatic circuit diagram of the circuit above
jeff-o (author)  tejask2 years ago
It's right there under the text, called "laser guitar.sch." You will need Cadsoft Eagle to open the file.
Krayzi992 years ago
Wow, man. You got skillz!
ccowsert3 years ago
About how much in total, minus the guitar, does this cost to build? i'm interested in making one as a senior project for school. And is there somewhere i can find the parts list?
my bad, i hadn't read the comments far enough
jeff-o (author)  ccowsert3 years ago
No problem! But you may want to hold off for a week or two. I've got something coming that I think you'll want to build instead!
News?
jeff-o (author)  renavspainatal2 years ago
I totally failed to get my updated guitar ready in time for the Epilog contest. That, and I was busy building a second storey on my house. It's been finished for a while now, though I couldn't find any musicians who were willing to play around with it for more than an hour or two (somewhat disappointed about that, actually). I needed someone to film showing what it can do since I can't play myself.
:/
I imagine how frustrating it is.
I hope you can find someone to help you so you can upload the instructable.

I think I'll wait for the next one then. =)
gr3ml1n jeff-o2 years ago
Whats the word on this alternate build?
This is AMAZING!

I want someone to play "Derezzed" by Daft Punk on this beauty. Or even better, interface it with a solid state tesla coil!!!!!!
I love the project, and i'm not sure if anyone has called you out on this, but it is a bass, not a guitar, 4 strings!!!

Thats all, i would love to make one though
jeff-o (author)  Max "the bassist" Pratt3 years ago
Well, it was made from an old bass, but what makes it a bass guitar? The length of the neck? The tuning? The number of strings? A tenor guitar only has four strings, yet it is not a bass.

Really, the Prism can be whatever guitar you need it to be... within the confines of four strings, of course. ;)
well measure for me the scale length (from the two points the strings touched the bridge and nut.) If it is 34 inches, it is a bass, also it should have about 20-24 frets. Tuning does not matter, because you can tune any instrument to achieve any tone you want.

A bass guitar is just the term for an instrument with all of those qualities, and it is really just a name.

Please do note however, that you do not play "chords" in the same was as you would for a guitar. A bass is one note plucked at a time, however sometimes one can play the octave of a note at the same time as the original to achieve the correct tone.
One other thing, your "victim" included standard P-Bass pickups in the hum-bucker layout, also a thumb rest below the strings. Both of these are used in basses, not guitars
jeff-o (author)  Max "the bassist" Pratt3 years ago
Well, it definitely used to be a bass. And it used to have frets, and strings, and pickups, and a thumb rest. Is it a bass if all those have been removed? It's kind of in a gray area, I think. As far as sound is concerned, it's more like a synthesizer or theremin...
scrpn17w3 years ago
I was just curious, what exactly do the connectors in the schematic hook up to? I am currently bread boarding this project and have no idea what to connect each of the plugs to.
jeff-o (author)  scrpn17w3 years ago
Most of the connectors are labeled in the schematic and ought to be self-explanatory (but ask me if they aren't!) The trickiest ones are the two switch potentiometers, which have a switch and pot integrated into a single unit. The steps that describe those components may help.

If you need full-scale drawings or the original schematic, send me a PM with your email address and I'll send them to you.
scrpn17w jeff-o3 years ago
I meant what do the "jp" plugs in the schematic get plugged into? Specifically jp3, jp4, jp5.
Also, what does the "Thermal Connection" note in the schematic mean?
jeff-o (author)  scrpn17w3 years ago
The two components must be physically touching, preferably with a layer of thermal paste between them.
jeff-o (author)  scrpn17w3 years ago
Ah! Those go to the rotary switch. It switches between sine, square and triangle waveforms. Step 7 has details on how to wire the switch itself.
Is it me or those schema and part list do not work, it ask me witch program I want to use to see it, have an idea guys?
jeff-o (author)  theunexpector3 years ago
To view the schematic you'll need Cadsoft Eagle, get it at www.Cadsoft.de. Or is your problem that they are downloading as .tmp files? In that case, try renaming the file to what it was supposed to be.
You would destroy such a beuty!!!!!

Just kidding nice project, might work on a variation as a side project =D
I cant seem to open laserguitar.brd, laserguitar.sch, & prism parts list! Can U help me out?
jeff-o (author)  youngcustoms3 years ago
.brd and .sch are Eagle CAD files; get a free copy of Eagle at www.cadsoft.de. The parts list is .txt, that shouldn't be a problem... Or are you getting .tmp files? Try renaming them as appropriate. If that doesn't work, let me know and I'll email them to you.
Sorry, I still having trouble with these!
jeff-o (author)  youngcustoms3 years ago
Well, describe the trouble and I'll try to help...
ArtXander3 years ago
Great man!!
Andreonh3 years ago
How glossy would the paper need to be because im wondering if i am going to need to buy some very glossy paper online?
jeff-o (author)  Andreonh3 years ago
You shouldn't need to go online to find the paper. Glossy photo paper works well (I use paper marked "high gloss"), others have had success with glossy magazine covers.
Andreonh jeff-o3 years ago
does it matter how long after i print it that i actually iron it onto our copper?
jeff-o (author)  Andreonh3 years ago
I'm not sure. I always did the transfer within hours, to avoid the possibility of scratching the toner off the paper.
Andreonh jeff-o3 years ago
using these exact instructions i did this "laser printer and all" and i ended up with a barely transfered ink. this is very strange... are you sure it doesnt need to be an inkjet printer
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