[sdiy] Unusual BP filter - Voltage Control

[david wright]

thanks to everyone for helping improve this
great filter - i wish you all had one.

i'm going to try 8 matched vactrols first - four for each pot
and see how it sounds. this seems to be the most
in tune with 1950s thinking. i like the idea of EL panel
alot - but i would have to make an additional 'break out'
box to house power supply, tubes and controls to power the ac input.
so i think i'll pass on that for now. this sucker is allready
a 'space heater' and i live in the desert.

if the 8 vactrols does not sound so hot - i will try the idea
of pww each of the vactrols' lamps via a PIC. i wonder if
i can run a pic off the heater voltage? ;)

thanks again

dave wright

ps - neon light bulb multivibrator w/ controls!
www.carrionsound.com/neonvibrator.mp3

----- Original Message ----- 
From: "harrybissell" <harrybissell at prodigy.net>
To: "david wright" <bastardita at hotmail.com>
Cc: <jhaible at debitel.net>; <synth-diy at dropmix.xs4all.nl>; "KA4HJH" 
<ka4hjh at gte.net>
Sent: Tuesday, September 14, 2004 10:20 PM
Subject: Re: [sdiy] Unusual BP filter - Voltage Control


> It depends on how fast you like to modulate the center frequency
>
> Vactols are good for slower motion, matching is tough but once you do that
> you could pass anything through it.
>
> EL panels could have higher speed, otoh harder to drive.  I'd think whis 
> would
>
> be second choice.
>
> PWM of analog switches would (imho) change the character of the filter a 
> lot.
> For a LPF maybe, for a BPF I'd avoid it.
>
> Now an interesting idea would be to use the PWM to drive the LEDs in the
> Vactrols... have 8 separate PWM outputs and a linearization table for each
> Vactrol. Make the matching REALLY good.   The Vactrol slowness would
> probably filter the PWM WAY WAY better than the analog switch method
>
> H^) harry
>
>