Synth-DIY Yahoo! Groups Archives

Re: [motm] fixed filter bank development.

2000-04-07 by jhaible

> I'd like to hear how this project goes. As far as a MOTM fixed filter bank
> goes, I remember the suggestion, "why not just buy a third octave graphic
> EQ?" They do make these pretty cheap now.

Because a filter bank and an EQ are very different beasts.
An EQ normally has symmetrical gain / attenuation, with typical values
of +/-12dB or +/-20dB or +/- whatever.
A filter bank such as the Moog Fixed Filter Bank or the EMS 8 Octave Filter
Bank allows attenuation of a single band as low as zero (or "minus infinite
dB").
Both the sound, and the implementation are very different.

BTW, I have built a clone of the EMS filter bank many years ago, and it
sounds wonderful. Filters are not as steep as the Moog's, but it's very
smooth and "musical".
I've added some patchpoints and overall level controls in order to get
dynamic control over individual bands with external VCAs. It's part
of my JH-3 Modular. I don't have a picture of the filterbank, but you see
a tiny part of the front panel on this picture:
http://www.synthfool.com/diy/hj7m.jpg
(on the right side, in the middle)

JH.

RE: [motm] fixed filter bank development.

2000-04-07 by Dave Bradley

Welcome to the MOTM list, JH. Your 440 design sounds wonderful! I can now
get those fat brass sounds with my MOTM that I've been waiting for.

Dave Bradley
Principal Software Engineer
Engineering Animation, Inc.
daveb@...

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> -----Original Message-----
> From: jhaible [mailto:jhaible@...]
> Sent: Friday, April 07, 2000 3:30 PM
> To: motm@egroups.com
> Subject: Re: [motm] fixed filter bank development.
>
>
> > I'd like to hear how this project goes. As far as a MOTM fixed
> filter bank
> > goes, I remember the suggestion, "why not just buy a third
> octave graphic
> > EQ?" They do make these pretty cheap now.
>
> Because a filter bank and an EQ are very different beasts.
> An EQ normally has symmetrical gain / attenuation, with typical values
> of +/-12dB or +/-20dB or +/- whatever.
> A filter bank such as the Moog Fixed Filter Bank or the EMS 8
> Octave Filter
> Bank allows attenuation of a single band as low as zero (or
> "minus infinite
> dB").
> Both the sound, and the implementation are very different.
>
> BTW, I have built a clone of the EMS filter bank many years ago, and it
> sounds wonderful. Filters are not as steep as the Moog's, but it's very
> smooth and "musical".
> I've added some patchpoints and overall level controls in order to get
> dynamic control over individual bands with external VCAs. It's part
> of my JH-3 Modular. I don't have a picture of the filterbank, but you see
> a tiny part of the front panel on this picture:
> http://www.synthfool.com/diy/hj7m.jpg
> (on the right side, in the middle)
>
> JH.
>
>
>
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RE: [motm] fixed filter bank development.

2000-04-08 by Tkacs, Ken

Yeah, the Moog 914, for instance, used LC filters. A single band of this FFB
consisted of a Level pot, a trimmer, three resistors, two caps, and two
coils. The caps were hand selected (as were two of the resistors on the
Lowpass cahnnel).

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-----Original Message-----
From: jwbarlow@...
To: motm@egroups.com
Sent: 04/07/2000 5:33 PM
Subject: Re: [motm] fixed filter bank development. 



How steep are the Moog's? Didn't they use LC filters or something
equally 
strange?