ARP VCF

[Thierry Rochebois]

Hello,

I received a copy of the US Patent 4011466 a month ago. It is the ARP
patent for their famous filter. They claim to have a signal/noise ratio
of 60 to 70 dB as to compared to the conventional "ladder type" 45 dB.
They also claim to have good resonance condition (so that you hear the
signal even with strong res).

It is based on a four stage design, each stage is composed of a PNP differential
pair that feed the inputs of LM3900 Norton amplifier.
I am not familiar with the Norton amplifier, I only know that it work like
a opamp but with current rather than voltage ;-)


The schematic and text describes almost everything excepted various component
values.

Does anyone own, or knows where to find a complete schematic, for this filter ?
Does anybody experimented with this design ?

Kind regards,


Thierry Rochebois
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