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Synthetic Music Systems

SMS BOB Midi-fied


MIDI-fying BOB !!!

What? Modding such a rare piece of equipment?? Hahaha, no one is as insane as me.
If Andy sees this, he might be furious! (Sorry, mate, I couldn't resist).
- I dun need to use the Kenton Pro-2 for just the SMS MARS. For the MARS, I just need basic Midi-CV/Gate and also maybe a few Midi CC->CV for controlling the filters and so on.
- The Pro-2 sitting above is taking up some space. I wanna put other racks there instead!!
I decided to open up BOB and take a look inside, since BOB is pretty much a passive patcher (except for the NOISE circuit)., and yes I'm right. There is enough space inside the BOB to accommodate a small Midi-to-CV Convertor.

Since I have BOB opened, maybe we should take a little peek inside!
Note: The securing screws aren't supposed to be loosened like that, I took the picture after I started taking BOB apart, heheeh!

This gives a rough idea of the PCB of BOB. Just basically a router.

On the right we see just this part has electronic components.
This is the Noise Circuit that provides the 3 Noises.

The close up of the NOISE Circuit.


MIDI-fying + Output Mod

bulletChoice of Midi-CV Converter: Doepfer MCV4
bulletAdd a 1/4'' Jack out at the back, simply duplicating the VCA minijack output.
bulletI have thought of a few ways, like removing some of the front sockets and mount in switch-sockets, but I didn't want to temper with BOB too much. So I decided that the CV coming from the MCV4 will be just simply tapped to the patchpoints.
bulletMCV4 has 3 extra Midi CC-CVs. One goes to the Filter CV. The other 2, I decided to goto the VCLFO MOD and the VCO MOD. But in case, I want switches to switch them off.
So far so good, fairly simple.

The Doepfer MCV4 is pre-configured / pre-tuned before I started any modding. This way, once the mods are done, I can easily test and finish things off. Don't have to dealt with tuning and config while testing for any faults of the mods.


Midi In and the Output Socket mounted at the back

Midi Blue LED and Learn Button mounted on the right of the front panel.

Switches above the VCLFO CV and the VCO MOD.

Output Routing

I drilled 2 tiny holes on the PCB next to the VCA Output socket and soldered a connector there.

Other CV/Gate Routing
Basically wires were soldered to the foil side of the PCB then I routed them back to the top.
I mounted a small stripboard with a connector there:

The other side of the connector goes to the CV outs from the MCV4 and the front switches.




The whole modding process didn't take long - it's more like re-routing things.

Now BOB has MIDI and a 1/4'' Jack Socket Output!

The 2 switches are pure On/Off switches that allow the Midi-CVs to go thru.
Anything patched to the BOB will still goes thru...
Or, the front sockets could be used as CV OUTS to drive other stuff, I suppose!

Midi Indicator (Blue LED) and the Learn button.

So basically that's it, simple!


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