[sdiy] Anyone recognize this schematic? It's a transistor ladder with PNPs...

[Tim Stinchcombe]

Hi Aaron,

> I found this interesting schematic while I was sorting 
> through files - but I can't remember where I got it from, and 
> my google fu has failed me!
> 
> http://users.ece.gatech.edu/~lanterma/ems11/CFR_ladder.gif
> 
> Did one of y'all draw this?
> 
> Anyone recognize the handwriting?

As Harry has already pointed out, it _used_ to be on the net somewhere, as I
have a copy too. I do note however that it is the same handwriting-style as
the Tau1010 on Jim Patchell's site:

http://www.oldcrows.net/~patchell/TAU1010/tauvco-b.gif

and I have it filed under 'Tau' on my PC (files are dated from 2007, so I
must have had recourse to go looking for something related back then!). How
similar is it to the  '1010' filter circuit?

> Almost every Moog transistor ladder VCF uses NPNs, but this 
> one (whatever it is) uses PNPs.

I also have a jpg file of an AM2100 PNP-based ladder filter, which I have
filed under 'Emu', which looks like it must have come from Rob Keeble's
Emulator Archive - however I cannot find it there now, so perhaps it was an
earlier attempt at reconstructing one of these filters (!?). It is entitled
'AM2100 LPF REV01B', dated 03/08/2005.

Tim
__________________________________________________________
Tim Stinchcombe 

Cheltenham, Glos, UK
email: tim102 at tstinchcombe.freeserve.co.uk
www.timstinchcombe.co.uk