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

[jeff brown]

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
> > >>>
> > >>>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >
>
>