[sdiy] Mathematics of flanging

[Tom Bugs]

This reminded me to dig back to see what PDFs I have on my hard-drive -- 
12 copies it turns out.. (16pages each).
There's so many interesting ideas in them! Really nice retro reading - 
some good circuit snippets etc.
I may get around to compiling them into a single PDF to send to a 
doc-printing company who'll spiral bind them - much nicer reading then ;)

Tom

On 05/03/2022 21:44, grant musictechnologiesgroup.com wrote:
> What the heck is Device Magazine? Sounds interesting of course.
>
> ------ Original Message ------
> From: "Pete Hartman via Synth-diy" <synth-diy at synth-diy.org>
> To: "Michael E Caloroso" <mec.forumreader at gmail.com>
> Cc: "synth-diy mailing list" <synth-diy at synth-diy.org>
> Sent: 3/5/2022 1:29:35 PM
> Subject: Re: [sdiy] Mathematics of flanging
>
>> Thanks for that Michael.
>>
>> I've tweaked the image so that the contrast is a bit more readable, I 
>> figured I'm not the only one whose vision needed such assistance, so 
>> here it is :)
>>
>> Pete
>>
>>
>> On Sat, Mar 5, 2022 at 12:57 PM Michael E Caloroso via Synth-diy 
>> <synth-diy at synth-diy.org> wrote:
>>
>>     Nice.
>>
>>     The key to extreme flanging sounds is inversion in place of the
>>     summing node.  Many delay units do not include inversion.  The
>>     inversion produces a radically different frequency response.
>>
>>     But a real "jet flanging" effect - same as the classic technique
>>     using analog tape players - needs a minimum of TWO delay
>>     elements.  The concept of the flanging effect heard by a listener
>>     in a fixed position relative to a jet airplane in motion was laid
>>     out in Electronotes #56 pg 12, so I attempted to implement it
>>     with my Korg SDD-3300, a very flexible triple digital delay.  See
>>     attached.
>>
>>     The result was flanging but the effect was mild. In Device
>>     Magazine volume 1:10:79 pg 10, Stephen St Croix - inventor of the
>>     CCD-based Marshall Time Modulator effect processor - lays out the
>>     crucial criteria for effective jet flanging effects.
>>
>>     Digital delays aren't ideal because you can't get deep enough
>>     modulation, the modulation LFO in digital domain is often too
>>     discrete at low sweep rates, and you need ~0.3ms delay (few
>>     digital delays offer short delay times).  BBDs aren't ideal
>>     because the amplitude of the direct and delayed signals must be
>>     matched within 0.1dB for widest notch bandwidth in the comb
>>     filter effect.  Also the bandwidth of delayed output must be as
>>     wide as possible for deepest nulls in the comb filter effect. 
>>     The deep nulls and wide bandwidth of the notches result in more
>>     extreme flanging effects.
>>
>>     Granted, from the Electronotes concept the two delays will need
>>     some filtering to emulate the two delay paths between
>>     listener and jet airplane, especially the reflected path.  Also
>>     the Electronotes concept does not take into account other
>>     indirect reflections.
>>
>>     The Marshall unit used CCD based delay elements to meet these
>>     criteria - dual independent delays, smooth/deep LFO modulation,
>>     wide bandwidth, and precise output matching.  CCD and BBD
>>     elements are bucket related, but operate differently.  Each
>>     sample charges the storage capacitor of each BBD element, while
>>     each sample DRAINS the charge of an initially fully charged CCD
>>     element.  CCDs are also much quieter.
>>
>>     Effect connoisseurs report that the Marshall Time Modulator
>>     delivers the best "jet flanging" effect.
>>
>>     MC
>>
>>     On Sat, Mar 5, 2022 at 1:36 AM Lanterman, Aaron D via Synth-diy
>>     <synth-diy at synth-diy.org> wrote:
>>
>>         I just put together a lecture on that, if you’re into that
>>         kind of thing:
>>
>>         https://youtu.be/LRZW31_aAnE
>>
>>         Aaron Lanterman, Prof. of ECE, Georgia Tech
>>         My blog on Education and Innovation:
>>         https://edupocalypsenow.wordpress.com
>>         My blog on Electronics and Programming:
>>         https://lantertronics.blogspot.com
>>         My YouTube channel on Electronics and Programming:
>>         https://www.youtube.com/c/lantertronics
>>
>>
>>
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>
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