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

[phillip gallo]

I believe the PNP ladder graphic image may have come from here:

http://www.sdiy.org/philgallo/CFR_ladder.gif

I scanned it from an old CFR catalog.

It was from a kit which only provided the components, you were
expected to build the filter upon Vector board or a self-made board.
I suspect the reason the filter was realized in PNP was to both be a
unique implementation and also to sell off the PNP's he bought in bulk
and spec'd to conform across the many synthesizer projects CFR made
available.

The late Charles F. Rogers was involved with Tau, (synth sub-modules),
Dynasyn (potted expo's and discrete OTA's), and CFR Associates (synth
kit's).

I visited him twice as he was supporting ARIES modules (and sold hard
to get parts from panels to semi's) after the firm crashed and burned.

I have wanted to scan a put the old "CFR Technotes" online but to date
i haven't.

regards,
p



 On Thu, Mar 31, 2011 at 3:07 PM, Tim Stinchcombe
<tim102 at tstinchcombe.freeserve.co.uk> wrote:
> 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
>
>
>
>
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