2040

[Mikko Helin]

Joachim wrote:
>First of all, thanks to Juergen for a wonderful 2040 schematic.
>(http://www.synthfool.com/diy/jh2040.gif)

Would it be possible to use that schematic to make a "real"
2040 clone, an IC with the same pinout as 2040 (not the VCF but 
just the gain stages)? How much does it cost today to start a 
production of IC's? Would it solve the Vbe matching problem, too?


-Mikko

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> Can the BC550Cs be replaced by transistors from CA3086s?
> /JB

I did some experimentation using transistor arrays for the
gain cells in a 2040-like filter a year back, or so. I used
Elantec EN2016 (NPN) and EP2015 (PNP) arrays, but the results
weren't that spectacular. The transistors in these arrays
aren't very well Vbe-matched (5 mV), which means that you'll
end up with a substantial amount of CV feedthrough at the output.

Desicrete devices can fairly easily be matched to 2 or 1 mV,
hence you'll have better CV rejection.

...