Analog Sound Synthesis on Your Computer

Like the sound of those old analog synthesizers? Want to play with one on your own time, at your own place, for as long as you want, for FREE? Here is where your wildest Moog dreams come true. You can become an electronic recording artist or just make some cool, trippy sounds to listen to on your mp3 player. All you need is a computer!

It's all done through the magic of a free circuit simulator called LTSpice. Now I know you're probably saying "Gee willikers, Tyler, I don't know anything about running a circuit simulator- that sounds HARD!". Don't worry, Bunky! It's easy and I'll give you a few templates to start with and modify to make whatever weird noises you want.

Not sure it's worth the effort? Here's a link to a ready to play sound file (it is made from "composition_1.asc" in step 7 of this 'ible) that you can try out. I converted it from .wav to mp3 to reduce the download time. http://www.rehorst.com/mrehorst/instructables/composition_1.mp3
There's some low bass in it the sound so listen with headphones or good speakers.

If you like what you see, vote for me!

Note: I have attached schematic files for LTSpice that you can run on your computer, but for some reason when you try to download them the names and extensions get changed. The contents of the files look OK, so after downloading the files just change the names and extensions and they should work. The correct names and extensions are shown on the icons you click to download.

Step 1 First things first

LTSpice is a windows program, but don't let that get you down. It runs fine under Wine in linux. I suspect there are no problems running it in VMWare client, VirtualBox, or other virtualization tools under linux, and probabaly on Macs too.

Download a copy of LTSpice for Windows (ugh!) here:
http://www.linear.com/designtools/software/ltspice.jsp

Install it.

What is LTSpice? It is a time-domain circuit simulator that every electronics hobbyist ought to know how to use. I'm not going to provide a detailed tutorial on how it works here, but I will explain a few things you'll need to know as we go along.

One word of warning- it is easily possible to produce frequencies that are too low or too high to hear. If you do that and drive your expensive speakers with a high powered amp you may just blow your speakers/amp to bits. ALWAYS look at the waveforms before you play them back and be careful to limit the volume when you play back a file for the first time just to be safe. It is always a good idea to play the files via cheap headphones at low volume before trying speakers.

Comments

[WineSoaked]

I would think that, for a musician's purposes, exporting the waveform in 24 bit, 96kHz would be more suitable format. Of course, whether real musicians would go to these lengths to generate music is another question :)

[Mark Rehorst]

You can specify 24/96 if you want, or even higher resolution than that. You'll also have to make the time step in the simulation shorter to ensure that your simulation generates a data point for each 96 kHz sample.

Musicians probably wouldn't bother, but it can be used to make a high resolution test CD or can be used as a signal source for electronic testing. It can also be used to test the response of a circuit you want to simulate, say a crossover for an audio system, etc.

[jstarkmuth]

Hmm, this looks like an interesting approach for very experimental music, but it seems to have a quite high "effort-per-result factor" compared to conventional "synthesizer construction kits" like SynthEdit, SynthMaker etc. So if someone is looking for an easier way to create your own software synthesizers, check those out.

[riverreaper]

could you post a video of its sounds?
ive a old casio im going to build something with im still in the research of the what all to atempt with it , i did manage to get all its components out 150 screws latter i put it back up on the thinking of what to do with it shelf lol

[LkArio]

Something that would be awesome is running it in realtime with a MIDI input

[LkArio]

Really awesome instructable! I had no idea a program like this existed, very useful.

[nb10]

This is great. thanks! For more advance sound design theory check out point blank online music production school

[Clayton H.]

can you play these through a midi keyboard?

[warossignol]

This looks like something I could have fun with. Only trouble is when I run te circuits I get a spice run error "trouble creating output .wave file" any suggestions ?

[Indiana jones]

change it to c:\windows\test.wav

[Mark Rehorst]

I got the same message when I tried to use a nonexistant directory to store the output file. If you don't have a c:\temp directory, make one and LTSpice won't have a problem creating the file. I wouldn't recommend junking up your windows folder with what may grow to be a very large file. Use a temp directory so you don't have to worry about deleting its contents at a later date when you're cleaning up your computer and can't remember what or why about the file.

[Indiana jones]

if you clog up your computer, you clog up your computer. it doesn't matter where you do it

[Mark Rehorst]

If you want to put the files in your Windows directory you're welcome to do it, however, the Windows folder is already clogged up with malware called "Windows". Most people don't clean up their machines by deleting files in the Windows folder, but a "temp" folder is a good place to put temporary files because 6 months from now you can just delete them without a thought about what the files are and how they were generated.

[Mark Rehorst]

If you are using my .wave statement unedited, make sure that the c:\temp directory exists before you try to run the simulation. If you have edited the .wave statement to put the output file in your "My Documents" folder you may have a problem because of the blank space between "My" and "Documents". Are you running the program as an administrator on the computer? If not you may need to make sure you are an administrator.

[AlexisFromParis]

Hey!
My first post for 1 year that i read this fantastic website,
but i must say that your project is just
awesome ! and for both educational and experimental purpose !

Thank's a lot and BRAVO !
Alexis (from Paris, France)

[Mark Rehorst]

Merci beaucoup mon ami!

[rethinker]

Way to go Mr Phoenix-DIY. I especially like the idea of synthesing analog circuits to make "digital" music. Its like SteamPunk but for software. Does anyone know of any libraries of analog circuits that could be used.

[Mark Rehorst]

Figuring out how to get the behavior you want is half the fun. There are a lot of on-line circuit libraries that you can tap for circuits, but most of what you need for synthesis is right there in the special function modules. Horowitz and Hill's "The Art of Electronics" is a very good, educational reference. Those of you on a tight budget can check the usual on-line sources for that one... One thing I haven't figured out how to do (yet) is make a swept frequency filter. I'm working on that and when I figure it out I'll modify this 'ible with the how-to. I think a VCVS type circuit should work, with f0 controlled by a swept voltage source. A swept peaking filter operating on a pulsed source should sound real interesting. Unfortunately there is no way to have anything like a variable resistor that you can turn while the simulation runs. I'll add some more sources and envelopes as I generate them.

[alzie]

Hi Tyler You could use the SW(itch) component. Its resistance can be made variable with voltage. A pair of these can then be applied to any 2 pole active filter ckt. Better yet, you could use the BV or BI sources to create resistances. They can be self referenced. Ie. the BI current can be a function of the voltage across itself. An external control voltage can be multiplied in as well, to make them variable. The imagination is the limit. The problem is digging deep enough!

[Mark Rehorst]

I think that would work. I'll try to come up with a circuit and add it to this 'ible. You're right- the only limit is the imagination. All these voltage and current sources get hard to keep track of so when I figure out how to make subcircuits I'll make some standard synthesizer modules as subcircuits that can just be dropped into the schematic and wired together. Then just add a few parameters to control them and you're off to the races. I want to figure out a way to make a wide-band width phase shifter that is controlled by a voltage so I can play with some stereo effects. The sin/cos output from the mod2 component is cool but it would be more fun to shift the phase to any value. Keep checking back to this 'ible every few days as I add more sounds/components. TD

[alzie]

Nice ible on doing sound with it. Great job! I hope this inspires more people to learn to use spice. Ive been using LTS for 8 yrz now, and am Totally addicted to it. It is Thee Most verstatile tool Ever! Ive simmed mechanical and acoustic as well as electronic systems with it. You can even use it to lay out perf board projects. But, i havent tried its sound capabilities. Now off to try doing some sound synth! Thanx for your inspiration.

[Scurge]

Nice! I just started learning LTSpice before the end of last semester. This is a great I'ble.

[Mark Rehorst]

Thanks! I have merely scratched at the surface of the sort of fun you can have with LTSpice. Not only can you generate a .wav for output, but you can use a .wav file for input. That means you can "build" audio filter circuits and hear what the filter will do to the sound. You can test crossovers, notches, etc. without having to actually build them.

[Pard]

Can you fix the files? WhenI go to DL they are bad files or something

[Mark Rehorst]

For some reason the Instructables server changes the names and sometimes extensions of the files. The .mp3 file comes down with an .mp3 extension and it plays, but the schematic files, which are actually text files and can be opened, read and editied (though I don't recommend it) with any text editor, have both file name and extension changed. Just change the extensions to .asc when you save the schematic files to your computer and they should work OK. All the schematics should have a .asc extension. When you installed LTSpice it registered the .asc extension so once you change the extension from .tmp to .asc the file icon should change and if you click on it LTSpice should open and display the schematic.

[stephenniall]

Wow very very cool