The Diode-Ladder Sine Shaper - Introduction - Exploring Analog Audio Synthesis, episode 10

The Diode-Ladder Sine Shaper - Introduction - Exploring Analog Audio Synthesis, episode 10

As always, supporting materials are on the project GitHub: https://github.com/kennykb/kevins-cave-kludges/tree/main/Synth/Ep010_Sine_Shaper

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In this episode we start looking at one of the oldest ways to build a sine shaper: the diode ladder (or piecewise-linear circuit). We examine the history of the technique, then build up our own diode ladder design, starting from literally nothing and adding parts a few at a time. We simulate the partial circuit at everh step along the way.

We finish with a couple of sine shapers that appear to be producing low-distortion sine waves in simulation. One of them is our design. The other is from a textbook and is a design that I want to spend more time understanding fully, before I actually build and demonstrate a shaper.


TIMELINE

00:30 Welcome
01:35 Textbook circuit
02:15 PSA
03:55 History
07:17 The 0-diode ladder
07:49 One diode pair
10:50 Two diode pairs
14:26 Three diode pairs and beyond
17:14 Textbook version
18:09 Outro


CREDITS

Images:

"Golden Gate International Exposition 1939 Souvenir Book"
https://www.flickr.com/photos/tunnelbug/5420527316
Jonathan Haeber
Reproduction CC-BY-NC 2.0
https://creativecommons.org/licenses/by-nc/2.0/deed.en

"William Hewlett"
https://en.wikipedia.org/wiki/File:William_Hewlett.jpg
Hewlett-Packard Company Archives

"David Packard"
https://en.wikipedia.org/wiki/File:David_Packard.jpg
Marketing in Progress

"HP200A front panel" © 2010 Flickr user "Colin"
https://www.flickr.com/photos/woz2/4894406295/in/photostream/
CC-BY-SA-2.0 https://creativecommons.org/licenses/by-sa/2.0/deed.en

"Fantasia" poster, style B, 1940
https://commons.wikimedia.org/wiki/File:Fantasia_poster,_1940_(Style_B).1940.jpg
© 1940 RKO Radio Pictures, Inc.
Copyright not renewed

"Radio Operator, CPL John Robbins of Loiusville, Nebr. 41st Signal, 41st Infantry Div"
https://itoldya420.getarchive.net/amp/media/scr188-fb97ec
Signal Corps Photo: GHQ SWPA SC 43 5901 (T/4 Harold Newman)
Public domain US Government work

HP 202A exterior view
From "Operating and Servicing Manual for Model 202A
Low Frequency Function Generator"
https://hparchive.com/Manuals/HP-202A-Manual.pdf
© 1956 Hewlett-Packard Company
Copyright not renewed

"HP 320AR distortion analyzer"
courtesy of Hewlett-Packarrd Company Archives Virtual Vault
https://www.hewlettpackardhistory.com/item/expanding-the-catalog/

"HP 300A Harmonic Wave Analyzer"
courtesy of HP Memory Project
https://hpmemoryproject.org/news/300a/hp300a_page_00.htm

"HP Model 400A Vacuum Tube Voltmeter"
courtesy of HP Memory Project
https://hpmemoryproject.org/news/cat48/cat48_page_26.htm

'For Excellence in producton, Army Navy "E"'
https://itoldya420.getarchive.net/amp/media/for-excellence-in-producton-army-navy-e-nara-514282-34ad7f
US National Archives and Records Administration
Public domain US Government work

Partial schematic of HP 202A (vacuum tube version)
From "A New Generator of Frequencies down to 0.01 CPS"
Hewlett-Packard Journal 2:10 (June, 1951), pp. 1-4
https://www.worldradiohistory.com/Archive-Company-Publications/HP-Journal/50s/HPJ-1951-06.pdf

Schematics oh HP 202A (version with Si diodes)
From "202A Low Frequency Function Generator"
https://hparchive.com/Manuals/HP-202A-Manual.pdf
© 1959 Hewlett-Packard Company
Copyright not renewed

Music:

“Light Sting” Kevin MacLeod (incompetech.com)
Licensed under Creative Commons: By Attribution 4.0 License
http://creativecommons.org/licenses/by/4.0/

"Arpent" Kevin MacLeod (incompetech.com)
https://freepd.com/music/Arpent.mp3
CC0, https://creativecommons.org/public-domain/cc0/

“Apero Hour” Kevin MacLeod (incompetech.com)
Licensed under Creative Commons: By Attribution 4.0 License
http://creativecommons.org/licenses/by/4.0/


© 2025 Kevin B. Kenny