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

[harrybissell]

That is ABSOLUTELY correct !!!

(I just found it :^)

If anyone is interested I suppose I can redraw the schematic and make a table
of the parts values... although you gotta wonder about using the LM3900 eh ???
:^P

Actually there are 36 filters from 50Hz to 9005Hz - about 5 per octave

H^) harry

jeff brown wrote:

> I believe it was the June 1974 AES journal, Vol 22 No 5.
> He used 9 boards with 4 filters each.
>
> Jeff
>
> ----- Original Message -----
> From: "harrybissell" <harrybissell at prodigy.net>
> To: "Cynthia Webster" <cynthia.webster at gte.net>
> Cc: "Michael Baxter" <mab at cruzio.com>; "jhaible" <jhaible at debitel.net>;
> "diy" <synth-diy at dropmix.xs4all.nl>
> Sent: Saturday, February 07, 2004 9:15 PM
> Subject: Re: GIC String Filter - first experiments (was: [sdiy] FilterBanks
> & CSound)
>
> > 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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> >
> >