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

[mark verbos]

Harry has the Lm3900 surpassed the BBD as you most hated chip?



harrybissell wrote:

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