[sdiy] Buchla 296 lowpass topology

Matthew Arthur mathewarthurtech at gmail.com
Thu Dec 1 02:59:51 CET 2022

I think it's a 2 stage lc low pass filter followed by a modified active
bridged t.

 My simulation of the active stage shows that the addition of the 4.7u cap
and 8.2k resistor to ground change the bridged-t so that it allows some low
frequency signal through.

Very 1960s design. Can't really see why it was chosen though, seems a bit
overcomplicated to me

On Wed, Nov 30, 2022, 8:29 PM Lanterman, Aaron D via Synth-diy <
synth-diy at synth-diy.org> wrote:

> Taking a peek here:
> https://modularsynthesis.com/roman/buchla296/296%20Schematics.pdf
> 15 of the 16 bands consist of MFB bandpass filters.
> But the lowpass is… something else? Look at the far right where it says
> “alternate section for board 1” — anyone recognize that topology? I have a
> suspicion that it’s something standard that I’m just not seeing because of
> the way it’s drawn.
> Aaron Lanterman, Prof. of ECE, Georgia Tech
> My blog on Education and Innovation: https://edupocalypsenow.wordpress.com
> My blog on Electronics and Programming: https://lantertronics.blogspot.com
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> https://www.youtube.com/c/lantertronics
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