[chuck-users] what exactly is tuned feedback?

[Casper Schipper]

Dear Michael,

>From the description it looks like a feedback delay (= comb filter) with
another (lowpass) filter in the loop. This type of feedback network can be
used like a basic (perhaps even simplistic) physical model of vibrating
objects like strings, collumns of air in tubes etc. The general term is
waveguide synthesis.  A feedback loop with a lowpass in the feedback is
often used to produce plucked string like sounds.  Karplus-Strong synthesis
is the original name for one particular efficient implementation of it
(using a simple 2 sample averaging as the lowpass filter, and filling the
delay line with noise at the start). You can also have really nice affects
adding some distortion or wave shaping in the loop (x - x^3 etc..). Chuck
is a really great language for building these things, since you can easily
write your own filters and shapers using Chugen, or Fauck (Faust for
chuck). But Faust takes a little more reading to understand in my opinion.

If your interested to dive deeper, there is an excellent online book by
Julius O Smith III, which starts with very simple models and goes into very
detailed models of a lot instruments (reeds, drums, flutes etc). His work
also formed the basis of some of the STK Ugens in ChucK:
https://ccrma.stanford.edu/~jos/pmupd/Strings.html

best,
Casper



On Wed, Oct 11, 2017 at 10:22 PM, Michael Heuer <heuermh at gmail.com> wrote:

> All,
>
> The Dave Smith DSM03 Feedback module has what is described as tuned
> feedback
>
> https://www.davesmithinstruments.com/product/dsm03-feedback-module/
>
> I have the same question as was posted here
>
> "I'm trying to understand what 'tuned feedback' means -- does this mean
> the signal enters a delay line that lasts one cycle of a certain pitch?
> (So, say, a 50Hz sound is a 20ms delay line.) Does this end up reinforcing
> that pitch when you hear the sound? (I guess it would reinforce multiples
> of the pitch too, but less so.)"
>
> https://www.kvraudio.com/forum/viewtopic.php?p=1673572&sid=
> ae6a060ebaffea267114c1b6b5edde68#p1673572
>
> Thanks!
>
>    michael
>
>
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>
>


-- 
Casper Schipper
casper.schipper at gmail.com
+31 6 52 322 590
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