Moog VCF Transistor Matching Question

[Martin Czech]

:::My friend Tim Caswell, who is the designer of all the Studio 
Electronics 
:::synthesizers (SE-1, ATC-1, OMEGA-8 polysynth), has told me that they 
match 
:::each of the 10 transistors in their ladder filters, using the same 
circuit 
:::found in the Moog service manuals.  He also said he's not sure how much 
:::difference it makes...
:::
:::Michael Bacich


Makes sense to me. Think you were running a small production line back
in 68 or so. Overall semiconductor quality was not as good as today, and
a grossly out of spec npn will sure make the cascade fail. So you have
to do tests for each component, anyway, or desolder, which you certainly
want to avoid by all means. I do this on my workbench as well. Soldering
in a broken transistor is so much trouble that I better check before.
If you test it, you can bin it, ie. sort them. The finer the bining grid
is the easier to match afterwards.  So for practical reasons I'm sure
the transistors were tested, and more or less matched and the upper and
lower pair may have been "better matched" then.


m.c.