Not surprisingly there is a very small amount of information on Buchla 200 series DIY modules. I imagine part of this has to do with the rarity and cost of the instruments in the first place. not a lot of folks trying to build to save money have $1.5K modules in their systems. But there are a number of other philosophical and practical reasons as well.
The Buchla 200e system is unlike any other modular. It has a complex series of internal busses and a computer that talks to all the different parts. Even highly professional 200e gurus and manufacturers such as Eardrill or Mark Verbos do not make modules in their series that are compatible with these connections. So, out of the gate we must concede any DIY attempts at modules will not truly be 200e compatible. Which is to say they will not talk to the preset manager among other internal things.
There also is the issue of the Buchla 1.2 octave CV "standard". This is different than every manufacturer including long out of production companies and all Euro, Frac, 5U, and other formats. So without some math work VCO and CV ranges will not track exactly as an actual 200e module.
So, what is a simple DIY builder then left to work with?
The answer is actually quite encouraging: The Power Buss which does power "standard" +/- 15vt PCBs and modules. Manufacturers such as MOTM, Blacet, Modcan, and DIY PCB makers such as CGS, Oakley, etc all offer modules or PCBs that run off the same power values as the 200e. This then in effect gives us access to a wide variety of modules which could be made and installed in a 200e system.
I will leave the philosophical discussion of what "should or could" be built into a 200e for a later post but concentrating on just the practical aspects of DIY Buchla modules let's start with the basics...
All DIY and manufacturer synth modules run off a positive (+), Negative (-) and Ground (gnd) connector. the two most common power ranges are the 12 volt Euro Standard (created by Doepfer in the 1990s) and the 15 volt MOTM/Blacet four pin standard. Since the four pin molex connector is usually used on 15 volt compatible to 200e modules and is readily available on most DIY PCBs I use that as the basis for my Buchla DIY modules.
The fun comes in when we look at the Buchla power and buss connector board. This is a very different looking beast but it's strangeness need not intimidate use as all we are going to use it for is to grab those three common connections for powering our module. I'm talking about the (+,-,and Gnd) connections.
The Buchla Buss and Power board and connector used in their cases and boats looks like this (The internal buss board is on the Left, a Buchla 200e module connector is on the right)
Thanks to the DIY community and Buchla aficionados we know the pin breakouts and part numbers for all these goodies. I got this from Aaron Lanterman's Buchla Tech notes webpage which also quotes Chris Muir of Eardrill. This link is a godsend for making the 200e innards and parts understandable.
"Power on a Buchla module is delivered from a dangling connector. There is a somewhere between a foot and a foot and a half of wire dangling from a module (strain relieved, of course) that terminates in an edac 306-010-500-102 connector.
1 Black: quiet ground 2 White: -15 3 Red: +15 4 Dark Green: +12 5 Orange: +5 6 Brown: noisy ground 7 polarizing key 8 Yellow: i2c clock 9 Green: i2c data 10 nc"
Don't worry if that sounds confusing. All we need for our basic purposes is the first three pins:
So if we wire out "standard" four pin molex connector to the Edac 10 pin Buchla connector it looks something like this:
Pin 1 = Gnd (Green)
Pin 2 = - 15vt (Black)
Pin 3 = +15 vt (Red)
Eagle eyes may notice the Edac 306-010-500-102 has ten connections and the Buchla Pin out above only lists 9 connections. This is because if you look at the 200e power board there is a notch at pin #7. I assume this is to make sure you only install the connector the proper way with pin 1 on the connector lining up with pin 1 on the power board. As you can see on the connector I used I marked this slot and cut off the pin so I would be sure to not reverse the connection.
The finished connector going from the four pin molex connector to the 10 pin Buchla Edacconnector looks like this:
(Note the notch lining up with pin #7 on the Buchla connector and Buss board)
All the standard disclaimers about doing this at your own risk, building, playing with power supplies and electronics apply here. Do NOT do this unless you have knowledge and experience making modules and with power supplies, connectors, soldering, etc. You are 100% responsible for your own music so you're 100% responsible for your own instruments as well.
To emphasize this a bit more consider outside of heath and other issues it's one thing to burn out your DIY module that cost parts and time. It's another to damage your $10k++ Buchla system and void your warranty. I did a world of testing the module with an external +/1 15vt power supply and then tried it out with my Frac panel and Modcan A System quite a few times before I plugged it into the 200e buss. And I started with a pretty much already self contained and assembled PCB (see THIS post for details) to go even slower. I am happy to report everything works and sounds great.
Stay tuned to this blog for other posts in the DIY series which will on both some tech points as well as ideas for modules which might compliment the 200e from outside manufacturer's of PCBs and Kits.
Solder an Soldier on!