GIC String Filter - first experiments (was: [sdiy] FilterBanks & CSound)

[harrybissell]

To boldly go where some men have gone before (but not in quite some time :^)

Ralph W. Burnhams did a project in the early 70's using multiple BPFs made from
(yuck) LM3900s... it was published in the Journal of the Acoustical Society of
America
or the Audio Engineering Society...

...sorry I forgot which. He had like 40 filters as well...   I'll see if I still
have the photocopies
and get some dates

Another of his projects was "TTL devices for monophonic synthesis" which may have
inspired the WASP design

H^) harry

Cynthia Webster wrote:

> on 2/7/04 4:35 PM, Michael Baxter at mab at cruzio.com wrote:
>
> > JH,
> >
> > Way cool sound, amazing!
> >
> > On the second sample, after the 40-bank GIC filter was turned on along
> > with the parametric, a little while in, the sound to me was distinctly
> > like a hammered dulcimer. Very nice rings and percussive timbres.
>
> > Best,
> > Michael
>
> Great Job Jurgen!
>
> Delightful, those same "rings and percussive timbres"!
>
> Cynthia
>
> >
> > On Sat, 7 Feb 2004, jhaible wrote:
> >
> >> Hi,
> >>
> >> I've finally made my own version of a String Filter Bank.
> >> Samples from some first experiments are avaiable at
> >> http://home.debitel.net/user/jhaible/jh_string_filter.html
> >>
> >> I think the peak/valley ratio of the main filter bank is ok,
> >> but the air/wood/bridge resonance needs some more
> >> adjustments. Any hints how to improove this are welcome.
> >> (Benade gives detailed information about the frequency -
> >> 125Hz, 175Hz, 1.5kHz and 2kHz for Cello -, but not
> >> about Q and Gain.)
> >>
> >> JH.
> >>
> >>
> >>
> >>
> >>
> >> -----Ursprüngliche Nachricht-----
> >> Von: Ian Fritz <ijfritz at earthlink.net>
> >> An: Tim Ressel <madhun2001 at yahoo.com>
> >> Cc: <synth-diy at dropmix.xs4all.nl>
> >> Gesendet: Mittwoch, 11. Dezember 2002 04:26
> >> Betreff: Re: [sdiy] Filter Banks & CSound
> >>
> >>
> >>> Tim --
> >>>
> >>> Filter bank references:
> >>>
> >>> "Electronic simulation of violin resonances," JV Mathews and J Kohut, J.
> >>> Acoust. Soc. Am., vol. 53, 1620 (1973).
> >>>
> >>> "Audio engineering improvements for clavichords," RW Burhans, J. Aud. Eng.
> >>> Soc., vol. 23, 635 (1975).
> >>>
> >>> "Filter bank design," IJ Fritz, Electronotes, #107, 16 (1979).
> >>>
> >>> "A 39-channel variable-Q filter bank," BA Hutchens, Electronotes, #115, 3
> >>> and #116, 3 (1980).
> >>>
> >>> It's the peak-to-valley ratio that mainly characterizes the overall
> >>> sound.  This ratio is strongly influenced by the shape of the resonance
> >>> curves and the number of resonators, since many long tails can add up to
> >> an
> >>> appreciable contribution.
> >>>
> >>> I used a single transistor circuit for my resonators -- just a phase-shift
> >>> oscillator with a bit of degeneration to set the Q.  I started with
> >> nominal
> >>> Q values around 20, but had to increase this somewhat to get 10 dB
> >> contrast
> >>> with all the bands turned up.  My design has variable amplitude on each
> >>> filter and variable Q in sub-banks of six frequencies.  That way I can --
> >>> for example -- do some formant shaping at low frequencies and timber
> >>> enrichment at high frequencies at the same time.
> >>>
> >>> The hollow, echoey sound you describe is from too large a peak-to-valley
> >>> ratio.  Several people have remarked on this before.
> >>>
> >>> Ian
> >>>
> >>>
> >>> At 07:50 PM 12/10/2002, Tim Ressel wrote:
> >>>> Ian,
> >>>>
> >>>> Yes, in fact Dr. Matthews was mentioned in the
> >>>> article. I'd love to see the article if you can lay
> >>>> your paws on it.  What kind of filters are in your
> >>>> filter bank? What frequencies and Qs??
> >>>>
> >>>> By the by, the CSound filters I used did not seem to
> >>>> parallel well. I didn't get that timbre change for
> >>>> slight frequency changes. Also the bank had a hollow,
> >>>> echo like sound. If I knew the real filters used I
> >>>> might be able to get it working better.
> >>>>
> >>>> --tr
> >>>
> >>>
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> >