[sdiy] Re: Another view to: Doepfer A-105 looks like Oakley Multiladder?

[Tony Allgood]

Hi Florian and all,

Please please do not kick up any fuss over this, it isn't really that
important. It happens all the time in industry. It is not illegal. I
have stated that I was merely disappointed that a fellow modular builder
has seemingly borrowed so heavily from mine.

>The first:  Beside the Oakley Multiladder and the A-105, I remember two
other filters with the identical feature...

You can go back a lot further than this. The Oberheim Xpander used an
OTA based CEM filter chip to do the same thing.

>The second: Inspired by the Formant 24 dB VCF...

I think this was two state variable filters which do not produce the
same effect as cascaded CR stages. OTA based designs, and the ladder, to
a certain extent will produce the correct responses neccessary for this.

>A insert for the Feedbackloop exists as pin contact on nearly every
Doepfer Filter PCB (as far I remember also on the MS404).

This is new to me, and many others on the list, and it was this point
that I formulated, along with many, that Doepfer's design had been taken
from mine.

I have also been told that somebody actually asked Doepfer to do multi
tapped filter around the time the SuperLadder came into being. It could
well be a coincidence.

But I must re-iterate that as a standalone module the A105 looks very
similar to my MultiLadder. I have no axe to grind, nor do I wish to
others to do it for me. But, I now feel that placing one's circuits on
the net as I, and many of list do, has now been put in jeopardy. Even if
the circuit has not been 'stolen', the perception is that it has, and
that is a real shame.

Regards,

Tony Allgood  Penrith, Cumbria, England

Oakley Modular Synth and TB3030:
www.techrepairs.freeserve.co.uk/projects.htm
My music: www.mp3.com/taklamakan