[sdiy] Re: moog high pass

[Magnus Danielson]

From: houshu at muj.biglobe.ne.jp
Subject: Re: [sdiy] Re: moog high pass
Date: Wed, 30 Jul 2003 20:29:56 +0900 (JST)

> Hello List, 

Hi Hoshuyama-San,

> "Theo" <t.hogers at home.nl> wrote:
> >  -Simple as in adding inverted LP filter output to input signal to get HP.
> > Takes about one opamp and 3 resistors.
> 
> An example:
> 
>    http://www5b.biglobe.ne.jp/~houshu/synth/moritaVCF76.gif
> 
> I don't follow all the discussion.  However, the following schematics could be
> useful.
> 
>    http://www5b.biglobe.ne.jp/~houshu/synth/Vcfv0212.GIF

This is an self-explanatory picture of how the normal ladder can be converted
so that injection of signal may appear at any point in the ladder. Lovely way
of transforming the curcuit. Study and go forth!

>    http://www5b.biglobe.ne.jp/~houshu/synth/Vchp0302.GIF

This is a transformed ladder wich can be viewed as the same 4 RC-curcuits
connected in HP mode and where the transistors act as resistors into the
ground. If you convert those into resistors I think the rest of the curcuit
should become fairly self-explanatory.

> Don't ask me to explain how they work please ;-)

Thanks for refreshing our minds!

Cheers,
Magnus - going out to the garden again...