Just a few notes to the comments.
> It is just unfortunate that Jan had to do that before getting a reply from Robert.
I did send Robert a fax nearly two weeks ago. Except from a short excuse for having used exactly the same resistor and capacitor values (he did not apalogize for copying the entire schematics) he never showed any true will to settle this situation between gentlemen. I posted at Head-Fi after not having received any answer to my mails for more than a week.
> If you believe that your intellectual property was stolen and have been unable to get satisfaction from the other party then there's only one way to proceed in a professional manner - get a lawyer and pursue your case within the legal system.
Before taking a lawyer one should always weight the possible benefits against the losses. If Robert would only have sold 20 amplifiers, then the "damage" would be much smaller than the costs of a lawyer. If he would have sold 800 amplifiers then it clearly would be worthwhile taking one. Robert did not want to provide me with his sales-numbers and I'm pretty sure he was counting on it, that I would not be willing to take a lawyer because of the work and costs involved. It's not an uncommon policy of companies to try to get away with what they consider "minor" offences.
I only had one choice to get an impression of the sales involved, and that was by going public. Sorry, but I feel I simply had no other choice. Or should I simply have the situation rest?
Moreover, I do feel that there are moral issues involved that do concern Head-Fi. Especially in the DIY-forum there is a lot of exchange of technical ideas. These are generally free for personal use but not for commercial applications. The "DIY-FORUM RULES" clearly state:
" the practice of "cloning" a viable presently for retail sale commercial product is OK if it is for personal use ONLY and we invite photographs of your handiwork .
What is NOT allowed is the attempt to make a profit on the designs of others unless you have explicit permission from the designer/manufacturer to do so"
The actions of Headphonia clearly violates the "spirit" of these rules!
> Instead of a Head-Fi member. Who might have a pre-conceived bias in either direction. Might I suggest an independent Laboratory.
Again, the costs would most probably be much higher then the benefits. However, I do have a suggestion to all owners of an Headphonia amp that have some technical knowledge. I'm willing to send each of you the schematics of the amplification circuitry by mail so you can check for yourself whether your amp is a PORTA CORDA copy or not. You only have to promise not to make these schematics public. But of course people here will be interested in the results of your comparisons.
> After you told me you have a patent I answered you this patent must be confirmed so you can claim anything.
You concentrate too much on the patent. You not only copied the crossfeed implementation as found in the PORTA CORDA but also the entire amplification circuitry. Although not protected by any patent there are laws against that!
> Even in the future I will use open designs
I have no problem with that. But you seem to forget that the PORTA CORDA was never an open design. The schematics were never published so you must have them "recovered" by simply analyzing one of the amplifiers.
> and will adopt them
You did not adopt the schematics of the PORTA CORDA. You used it 1:1 (except for using a different opamp of course)
> (as every designer does).
Not true! I never analyzed any other amp. And I'm also very sure that people like Tyll Hertsens (who owns a CORDA HA-1), Ray Samuels (who owns two CORDA amplifiers, Rudi Stor (also a customer of mine), Michael Grace (who licensed the Crossfeed filter) and Norbert Lehmann (who I know well) never tried to copy any of my work or that of other people. These are all very nice people and I have great respect for their work, because they all make their own designs. I consider them colleagues and not just competitors. It's like a tennis-match. On the court you want to make the points but outside the courts you can be friends.