[sdiy] Legal issues of cloning

[The Old Crow]

   Well, since I did the crOwBX over the summer, I suppose I should 
address this issue myself.

   To me, a clone is a direct copy of a something.  The biological 
example being identical twins.  What I wanted was not a clone of the OBX 
in construction, look and feel but enough of a functional equivalent so 
as to in this case obtain the vintage OBX sound.  To that end, I had to 
make a number of design choices.  It did not need to be a 
programmable-preset machine.  It did not need to be in a stage keyboard 
enclosure. It did not need a CPU to oversee system operation.  CEM3310s 
were not going to be a viable solution for the EGs, so I crafted my own 
based on canonical ADSR designs along with the CEM3310's design basis as 
well described and implemented by JH in his VCHADSR project.  While 
CA3080s are out there again thanks to Rochester Electronics, I decided 
as Oberheim matched 3080s for the voice cards it would make sense to use 
the LM13600/700 as they're intrinsically die-matched.  I changed the 
discrete SEM-style VCOs to use better expo converters.

   In the end, a crOwBX voice card is about half "stock" and half new 
stuff.  I say "stock" because even the original OBX stuff needs some 
parts substitutions making it new old stock ;)  I also make no secret of 
where design ideas come from: I credit Tom Wiltshire for his noise 
generator PIC, JH for his VCHADSR notes, etc. in my schematics. Never 
mind Tom Oberheim who gets his own link  on the crowbx site.  Whatever 
"cleverness" I claim for myself, such as it is, is mainly in the 
squashing of the card form factor into a 10-board assembly that fits 
behind a 5U x 6U panel while still keeping the voice cards OBX 
retrofit-compatible.

   What I got in the end is what I wanted: a fully manual 4-voice 
SEM-style OBX sound before everything went all CEM chips.  I have no 
desire to commercially manufacture such a thing as it took me 4 months 
to craft *one* and with the man-hours either hired or invested 
myself---I can see why they cost $5500 in 1979.  I'll offer boards for 
DIY types, and that is about it.

   --Crow

   (For those who are asking "what the heck is the crOwBX" ... 
http://www.cs80.com/crowbx/ ;)

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