[sdiy] Reverse engineering a analog synth module?

[Bret Truchan]

Hello everyone!

I'm sorry to post so many questions.  You have all spoiled me with amazingly 
informative answers. :-)  Here's an interesting one for 'ya!!

I've been very happy and successful in building a few modules (for analog 
modular gear) so far.  My designs tend to be *very* simple.  I'm also 
focused on modules that deal with logic and microcontrollers [gate stuff].  
However, when I peer into my Doepfer system, even the most simple modules 
have more components than mine.  Which makes me wonder.... what's all that 
stuff for?!?   And, um, am I missing anything? The dual logic module comes 
to mind.  It looks like there's a microcontroller in there, and some 
resistor networks, but there's a plethora of other components that baffle 
me.

Can anyone explain what a typical TTL based analog module may have for basic 
components?  For example:

1. There are probably two or more capacitors for reducing noise on the power 
lines.  One of these will be located near the power input, the others near 
the vcc pins on the ICs.

2. There are probably going to be resistors to limit the current on the 
input and output jacks.  These may be in the form of resistor networks.

3. If you see zener diodes, they may be being used to limit voltage to a 
certain level.

Thanks a ton!  I don't suspect that anyone will *really* go through the 
gauntlet, but it sure would be sweet if you do!!  Schematics are nice, but 
usually when I see them, I'm like a little kid saying "why? why? why?" :-)

Cheers to you all.
- Bret

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