[sdiy] Unusual BP filter - Voltage Control

[david wright]

hey folks - i've used this filter in my studio for
several years now. great sound. talking with eric
i'm debating adding photocells for each gang
of the pots (2 pots) and a some leds to do this.

anyone else have any better ideas?

dave wright

----- Original Message ----- 
From: "KA4HJH" <ka4hjh at gte.net>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Monday, September 13, 2004 1:54 AM
Subject: [sdiy] Unusual BP filter


> Check this slightly complicated bandpass filter--it's tuned with an
> eight-gang potentiometer:
> 
> http://www.metasonix.com/krohnhiteFilter.gif
> 
> 
> Some comments from Eric Barbour:
> 
> Krohn-Hite 330A sweepable bandpass filter. 1952, all tubes,
> FIFTEEN tubes. Very difficult schema to find, very
> rare piece of equipment. NEVER used in recording
> studios, only in labs. Insane monstrosity.
> 
> It's the only way a WWII era engineer could think of.
> Four simple first-order highpass filters followed by
> four lowpass filters.
> It's not even a typical active filter circuit, though there
> is some feedback.
> It stinks of black-coffee-and-cigarettes thinking. Sort of like
> the ENIAC schematics I've looked at. Not elegant but works,
> more or less.
> 
> 
> Thanks to Dave Wright for the scan.