Controlling the A-100 via MIDI

In the beginning it was not difficult to pick a Doepfer MIDI-CV interface for your A-100 system.
The A-190 MIDI-CV/SYNC Interface was the only one available and there were not many other options.  (the A-191 MIDI-to-CV Interface / Shepard Generator was way more complex, i will discuss it in a future blogpost).
The A-190 is a powerful module that not only provides a few CV and Gate outputs, but also Portamento, Scale-settings, Pitch-bend, Glide, Clock and Reset signals, has a built-in (software) LFO and very flexible programmability.
Without a proper display it is quite awkward to program, but you'll quickly learn how to read the combinations of burning and flashing LEDs.
I do miss some further (software) development for this module. The arpeggio function, mentioned on the front-plate isn't even implemented (!)

A cheaper option that you can buy nowadays is the  A-190-2 Midi CV/Gate interface, which is based on the Doepfer MCV4. Only some minor changes were made for a better adaption to the A-100 system, e.g. five 3.5 mm sockets and zero-symmetrical CV for pitch bend, to be able to adjust the pitch bend range e.g. in combination with the precision CV adder A-185-2 and the glide function.
The module has no MIDI Thru and MIDI clock and reset functions though.

The new A-190-3 USB/MIDI-to-CV/Gate Interface that is in production stage has almost the same possibilities, but will be a modular version of Doepfer's upcoming Dark Link Module. This one will support USB and the release date for it is set for early 2011.
Another advantage of these two cheaper modules is that they don't need the additional +5V adapter. 

If you are looking for a polyphonic MIDI-CV contoller you will probably have to wait a while. Doepfer is busy working on the A-190-5, but it will be completely redesigned this year. A final version will  probably contain an LC display (similar to the A-187-1), some control buttons, a USB interface and higher resolution DACs with higher voltage range (probably 12 bit and 0...+10V). It will be a four voice polyphonic Midi to CV/Gate interface with 12 CV and 4 Gate outputs and different modes (e.g. unisono, four-fold monophonic, different four voice polyphonic modes.)

Tip: The monophonic MIDI-CV converters can write and read to the A-100 Busboard, more info on this HERE

Busboard Access

Updated August 25th 2011

A good patch can sometimes turn out to a whole spaghetti of patchcables.
Luckily Doepfer provided the A-100 system with a subsystem that makes the routing of some Gate and CV signals through the internal busboard-system possible.

It's too bad that not all modules have this ability, but for some modules this is a good way to avoid "over-wiring" your system with patch-cables.

Only modules A-110 (Standard VCO), A-111 (High end VCO), A-111-5 (Mini Synth. Voice), A-140 (ADSR), A-164-1 (Manual Gate), A-185-1 (Bus Access), A-185-2 (Precision Adder) and A-190-1,2,3 and 4 (Midi Interfaces) have access to the CV or Gate signal of the A-100 busboard.

The A-164-1, A-185 (-1 and 2) and A-190 (-1,2 and 3) can be used to "write" the busboard, i.e. they can output the signals to the bus.

The others are able to "read" the busboard, i.e. they pick up the signals CV (A-110, A-111, A111-5) resp. Gate (A-140, A-164-1) from the bus.
The A-111-5 can pick up CV and Gate from the bus. Also the planned A-143-4 Quad VCLFO/VCO will be able to read the A-100's busboard.
For details please refer to the user manuals of these Doepfer modules.

Most of the modules come with jumpers inside that can connect or disconnect the signal from and to the busboard. If other modules should be able to "write" or "read" the bus some of them can be modified. More on this in a future modding blogpost.

Doepfer warns on their DIY-site for shortcircuiting modules and/or busboard, so please take note:
Pay attention that only one module is allowed to "write" to the same bus signal.  If two or more modules write to the bus this leads to a short circuit of the corresponding outputs.
Please let me know if i forgot some modules in the Feedback section of this post, thank you!