Learning Computer Science Via Building Analog Synthesizers

This presentation is an alternate history of your own journey learning computer science. If you started learning all over again, and instead of reading books on C# development or watching videos about Vue.js, you decided to become a developer by building hardware analog synthesizers instead, what would the programming world look like to you? Imagine that the first computer you used was analog instead of digital, that you learned about abstraction from op amps instead of base classes, and you had to solve problems with an oscilloscope instead of a debugger. You might be very good at understanding computational abstractions! Building an analog synthesizer from electronic components is a fun way to learn about electrical engineering, but it also holds many lessons about computer science. In this delightfully strange talk, we will build several computational models from the transistors up, learn how to debug from first principles, understand dynamic typing in terms of modular synthesis, and also have a bunch of beeps, blorps, and solder.

Transcript

1. Craig Stuntz ∈ Improving Via Building Analog Synthesizers Learning Computer Science https://spe a kerdeck.com/cr a igstuntz
2. Disclaimer This talk is intended to be the strangest presentation at CodeMash. Should you fi nd that this is not the case, please approach the podium afterwords so that I can fi nd out who had a weirder talk and learn their secrets. https://www.tumblr.com/c a tsonsynthesizersinsp a ce/801547852561121280/erm a gerd-20-o ff -everything-s a le-now-on-just-use
3. I Built Am Building a Synthesizer
6. Five-ish Less Than Obvious Facts About Synthesizers https://www.tumblr.com/c a tsonsynthesizersinsp a ce/796655773470064640
7. How a Synthesizer Works (In one big oversimpli fi cation!) Oscill a tor Filter Envelope Gener a tor Ampli f ier
8. “Synthesizer” • Might be a n a log or digit a l • Usu a lly controlled vi a MIDI/USB • Often polyphonic “Modular synth” • Might be a n a log or digit a l • Usu a lly controlled by Control Volt a ge (CV) • Usu a lly monophonic https://oberheim.com/products/ https://commons.wikimedi a .org/wiki/File:C a t_modul a r_synthesizer.jpg
9. Make Music • Softw a re, integr a ted h a rdw a re • Complex • Non-modul a r • Often polyphonic • Complic a ted! Learn Electronics • H a rdw a re • Simple • Modul a r • Usu a lly monophonic https://u-he.com/products/div a /
10. Solder a Synth • Instructions focus on PC a ssembly • Pre-soldered SMD components • Designed to produce a more complex sound Learn Electronics • Instructions focus on le a rning electronics • Bre a dbo a rd- f irst a ssembly • Simple circuits
11. Some Things That Are Challenging Building a Kit • Le a rning to solder • Le a rning b a sic circuit theory • Le a rning how synthesizer circuits work • Debugging circuits when they don’t work • Designing a circuit which works in pr a ctice • Building synthesizer circuits th a t work in the re a l world, not just on a bre a dbo a rd • Le a rning KiC a d/designing circuit bo a rds Designing a Circuit
12. Real Synthesizers Are More Complicated Prior to the l a te 70s/e a rly 80s ➡Ne a rly a ll a n a log Tod a y ➡Mostly digit a l - However, new a n a log instruments a re still m a de - Hybrid instruments combine a n a log a nd digit a l processing https://commons.wikimedi a .org/wiki/ File:1st_commerci a l_Moog_synthesizer_(1964,_commissioned_by_t a a a a https://www. a rturi a .com/products/h a rdw a re-synths/microfre a k/overview
13. Imagine… https://www.tumblr.com/c a tsonsynthesizersinsp a ce/793753719502258176
14. What Even Is a Synthesizer? https://www.tumblr.com/c a tsonsynthesizersinsp a ce/792347529584001025
15. A Keyboard That Goes “Bleep! and “Bloop!” and “Plonk!” https://commons.wikimedi a .org/wiki/File:Bob_Moog3.jpg
16. A Synthesizer is a Function f(t) = amplitudet time → a mplitude →
17. A Synthesizer is a (Collection of) Functions […] etc. bell(t, inputs) = amplitudet piano(t, inputs) = amplitudet guitar(t, inputs) = amplitudet
18. A Synth Preset Is a Function Composition let bell = oscillator >> filter >> amplifier << envelopeGenerator
19. How Could These Functions Be Implemented?
20. A Synthesizer is a Function Two very common implementations • The synthesizer function c a n be implemented with a n a n a log computer An a log Oscill a tor An a log Filter Output Ampli f ier Digit a l W a ve Gener a tor Digit a l Sign a l Processor Digit a l to An a log Converter • Or a digit a l computer 🔈 🔈
21. Analog • Concerned with a n a log sign a l levels • Slow (such a s a udio/video) Hz-kHz Digital • Concerned with logic levels (on/o ff ) • F a st (computer clocks) MHz-GHz • Speci a lized tooling Analog Electronics 🤝 Digital Electronics • Built from s a me components — resistors, c a p a citors, etc. • To a l a y person the bo a rds look quite simil a r • At bottom a ll electronics a re a n a log! https://commons.wikimedi a .org/wiki/File:Digit a l-sign a l-noise.svg
22. Analog and digital synths are just functions from time to amplitude. They just use an analog or a digital computer, respectively, to do it.
23. Why Bother with Analog At All? Digital Analog
24. Digital Computing in 1956 https://commons.wikimedi a .org/wiki/File:Bendix_G15.jpg
25. Early Digital Synthesizers: Expensive++ https://commons.wikimedi a .org/wiki/File:F a irlight_CMI-IIx.jpg https://commons.wikimedi a .org/wiki/File:NED_Syncl a vier_VPK_%28Velocity_Pressure_Keybo a rd%29_1.jpg
26. Dawn of the A ff ordable Digital Synthesizer https://commons.wikimedi a .org/wiki/File:Y a m a h a _DX7_synthesizer_-_combined_im a ge_with_di a gon a l_ a nd_top_views.jpg
27. Analog • You must tune them, a nd it’s 😣 • Tod a y, rel a tively expensive to build or buy • More voices = more expensive Digital • No tuning necess a ry 😁 • You c a n ship new fe a tures in softw a re • More voices = m a rgin a lly more powerful computer Shouldn’t Analog Synths Be Obsolete? • Sounds a wesome!
28. Why Bother with Analog At All? Digital Analog https://www.youtube.com/w a tch?v=opQSGvPQHL0 Kenny Loggins, lol
29. Surely You Can Simulate Analog on a Digital Computer, Right? https://u-he.com/products/div a /
30. What Is the Point of Analog Synths in 2026? https://www. f lickr.com/photos/petergorges/2681345079
31. What the Hell Have You I Built? https://www.tumblr.com/c a tsonsynthesizersinsp a ce/802009448063303680/10-o ff - a ll-orders-with-code-everything10
32. Choosing a Synth to Build https://commons.wikimedi a .org/wiki/File:Bre a dbo a rd_full_plus.svg
35. … a nd a power supply!
41. Types
42. Let’s Make Some Noise!
43. Oscillator
44. VCA + EG
45. Filter
46. Control Filter
47. What Just Happened? This diagram is a convenient lie Oscill a tor (VCO) Filter (VCF)
48. Let’s Talk Cables
49. Let’s Talk Cables
50. A Better Way? NPUT UTPUT Audio sign a l Control sign a l
51. Models of Computation
52. Analog Synths & Digital Synths Analog Electronics & Digital Electronics Analog Computers & Digital Computers
53. von Neumann Architecture https://commons.wikimedi a .org/wiki/File:Von_Neum a nn_Architecture.svg
54. Logic Circuits
55. Quantum Computers https://www. f lickr.com/photos/feuilllu/46028735084
56. Analog Computers https://commons.wikimedi a .org/wiki/File:Antikyther a _Fr a gment_A_(Front).webp https://commons.wikimedi a .org/wiki/File:He a thkit_An a log_Computer.jpg https://commons.wikimedi a .org/wiki/File:099-ferreltpm.jpg https://uplo a d.wikimedi a .org/wikipedi a /commons/7/7e/AKAT-1.JPG
57. Abstraction
58. Structured Programming
59. A Black Box (actually cyan, but you get the idea) https://www.rol a nd.com/glob a l/products/gokeys_3/
60. Black Boxen
61. Zooming In…
63. What’s the easiest way to design an oscillator? Try to design an ampli fi er.
64. Analog Digital Oscillators let r a mp = 1.0 - ph a se ph a se += frequency / s a mpleR a te if ph a se >= 1.0 { ph a se -= 1.0 }
65. Analog Digital Filters func lowpass(inputSample: Float, cutoffFrequency: Float) -> Float { let normalizedCutoff = 1.0 / tan(.pi * cutoffFrequency / sampleRate let coefficientA0 = 1.0 / (1.0 + sqrt(2.0) * normalizedCutoff + normalizedCutoff * normalizedCutoff) let coefficientA1 = 2.0 * coefficientA0 let coefficientA2 = coefficientA0 let coefficientB1 = 2.0 * (1.0 - normalizedCutoff * normalizedCutoff) * coefficientA0 let coefficientB2 = (1.0 - sqrt(2.0) * normalizedCutoff + normalizedCutoff * normalizedCutoff) * coefficientA0 let outputSample = coefficientA0 * inputSample + coefficientA1 * previousInputSample1 + coefficientA2 * previousInputSample2 - coefficientB1 * previousOutputSample1 - coefficientB2 * previousOutputSample2 previousInputSample2 = previousInputSample1 previousInputSample1 = inputSample previousOutputSample2 = previousOutputSample1 previousOutputSample1 = outputSample return outputSample
66. Op Amps
67. Bu ff er Ampli f ier Inverter Inverting Ampli f ier Comp a r a tor Etc.
68. Feedback
69. FPAA Field Programmable Analog Array
70. Sequencing
72. Reverse Engineering
73. https://commons.wikimedi a .org/wiki/File:Minimoog_Voy a ger_Performer_All_White_circuit_bo a rd_-_Oscill a tor_section_ a
74. Reverse Engineering Firmware https:// a jxs.me/blog/Introduction_to_Reverse-Engineering_Vint a ge_Synth_Firmw a re.html
75. https://www.youtube.com/w a tch?v=XM_q5T7wTpQ
76. Debugging https://www.cockro a chl a bs.com/blog/gr a ce-hopper/
77. Printed Circuit Boards
78. Breadboards
79. A Bucket of Parts
80. Techniques If I put a broken circuit in front of you, could you fi x it? https://commons.wikimedi a .org/wiki/File:Cold_solder_joint2.jpg
81. Debugging Work fl ow 1. Look for “obvious problems” 2. H a ve a model of the thing I’m looking a t 3. Comp a re the observed beh a vior with the model 4. Try to reproduce the issue in isol a tion 5. When I f ind a devi a tion of the observed beh a vior from the model, try m a king a ch a nge 6. Observe if the ch a nge brings the beh a vior of the system closer to the model a nd keep it or revert it a s needed 7. If the circuit still does not work, go b a ck to the step 2 a nd iter a te until I h a ve a working system
82. Tools
83. Debugging Tools for Developers • Debuggers ( a t the risk of overst a ting the obvious) • Linters • Pro f ilers • printf • Rubber ducks https://www. f lickr.com/photos/bu ff a boy/29249589265
84. Debugging Tools for Electrical Engineers • Digit a l Multimeter • Oscilloscope • Audio Ampli f ier • Desoldering tools • Miscell a neous tools for speci f ic uses: • Logic probe • Component tester • LCR or ESR meter • Spectrum/network a n a lyzer • Etc.
85. Can I Do This?
86. If You’ve Never Soldered Anything…
87. Tools You Will Need • Bre a dbo a rd ($10-25) • Temper a ture-controlled soldering iron ($50-200) • Solder ($10-30) • Ventil a tion hood ($80, or work outside) • Multimeter ($50-200) • Oscilloscope ($350-800, buy used) • Wire cutters ($10) • Desoldering tool ($10) • Kits (€ 60.00/e a ch, € 630.00/system)
88. Live Demo
89. Want to Learn More? • Books/re a ding: • M a ke: An a log Synthesizers, by R a y Wilson • Electronotes, by Bernie Hutchins (https://electronotes.net f irms.com/free.htm) • Music a l Applic a tions of Microprocessors, by H a l Wilson (out of print) • YouTube series by: • Moritz Klein https://www.youtube.com/@MoritzKlein0/pl a ylists • Dr. A a ron L a nterm a n https://www.youtube.com/@L a ntertronics • C a ts on Synthesizers in Sp a ce (buy their merch!)
90. Who’s This Doofus? Director of Consulting, Improving https://cr a igstuntz.com cr a igstuntz@gm a il.com @Cr a igStuntz@discuss.systems