sue you, sue me

Joachim Verghese jocke at
Wed Apr 3 13:33:43 CEST 1996

On Tue, 2 Apr 1996, Matt Haines wrote:

> We've all heard how Roland was possibly sued over borrowing Moog ladder
> technology for their filters, but replacing transistors with diodes instead

I don't think this ever happened. There exists at least one patent
which describes the diode ladder filter, and it was not Moog's.
This patent was filed in March 1975 by Brian Walmann (never heard
of him before).

Moog's patent covers only the *transistor* ladder (and corresponding
highpass cascade). If he had used the term "silicon junction" or
similar, then his patent would probably have covered the diode ladder
as well.

Here's some info on the Walmann patent:

United States Patent  4,018,126
Title:     Tone generation and modification apparatus 
Inventors: Walmann; Brian I. (6823 N. Michigan, Kansas City, MO 64118). 
Filed:     Mar. 26, 1975

Last sentence of the abstract:

Among the novel functional modules utilized in the apparatus is an
improved type of low pass, electronic R-C ladder filter employing diodes 
and fixed value capacitances, rather than transistors or/and variable
value capacitances. 


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