This project has kept me busy for the past few months. It was suggested some while ago that I do a ModuleModule version of CVGT1 to go in a Buchla (see my earlier post). My initial thoughts were that it was probably not the best solution as front panel space in a ModuleModule is quite restricted and Buchla real-estate is not cheap. However what I didn't consider was that Buchla can also talk to Serge, BugBrand, Fenix etc and Serge users seemed to want this solution. Consequently I set about designing (or redesigning) CVGT1 to fit in a ModuleModule form factor. Chris Muir from Eardrill produced a great interface document which defines just about all I needed to know for designing a ModuleModule (I'll refer to ModuleModule as MM from now on).
Because of the smaller front panel space I had to lose some features i.e. scaling and offset on the Buchla to other synth CV channel but as it is in a Buchla and will interface to an external 1V/octave synth I've fixed the scaling at 0.8333 (1/1.2) and zero offset. The PCB design allows either 3.5mm jacks or 4mm bananas to be fitted; so one PCB can be configured to for Euro or Serge etc.
Clearly this design has PCBs parallel to the front panel unlike CVGT1 which has them perpendicular hence the change in jack style. The PCBs had a completely new layout with all front panel related parts on the first board (Front Panel Interface Board) and most of the circuitry on the second (Main Board). Here are some design images of the variants (there are a few very minor tweeks to the graphic since this was drawn and you'll see a few variations in the prototype pics below).
I built a prototype and that's all working nicely. Aside from the new PCB layouts I had to make some changes to the pulse/trigger/gate circuits to run from ±15V rather than ±12V but there were no major changes. Heres a scope image of the Buchla compatible pulse I achieved:-
Here's the prototype with an ink jet printed plastic overlay on the front panel.
All components are conventional through-hole types - I may go over to surface mount if I get more orders than I can personally cope with but think I will still retain through-hole if anyone fancies a kit. You will also notice that the scaling trimmers are front-panel accessible (with a small screw driver) however these are for very fine trimming ±0.5%.
The first pre-production modules will be available in just over a week when the screen-printed panels are in stock. I have a number of interested 'customers' that I will contact soon and will start a pre-order list; please feel free to contact me to get on the list: It will be a 'no-commitment no money up front' arrangement as before with CVGT1 and I will poll all interested parties in turn when I have a module ready to ship to see if you want one. I have not finalised a price yet but guess it will be in the same ballpark as Eardrill's own range of single panel medium complexity MMs.
It will be interesting to see how this takes off, CVGT1 started slow and now there are 200 out there with bags of interest still. I will do an update in the next week or so. Thanks for reading.
I was recently commissioned by a client to build a custom Euro Buchla interface module, similar to the two I previously built, but with offset switching. The previous two designs both had fixed offset and gain and were intended for use with envelopes, LFOs etc. In other words there was no 1V/octave to 1.2V/octave scaling required just offsetting to ensure the Euro signals stayed in the 0-10V range of the Buchla (you can refer back to my earlier post here).
This module is intended to be used alongside my client's CVGT1 module (which provides the ground reference connection) and adds more CV channels. My client uses Expert Sleepers' SilentWay software for pitch sensitive CV and was not interested in scale conversion as the software does the necessary recalibration however he also wanted the flexibility to be able to interface envelopes, transients and LFOs and so wanted to be able to DC shift signals when he needed to.
The spec was 4 channels of Euro to Buchla (scale of 1, 0V or +5V offset) and 1 channel of Buchla to Euro (scale of 1, 0V or -5V offset); so 10 connectors a 5 switches in 8HP.
My 8HP prototyping panels proved to be difficult as the existing hole positions meant that the connectors and switches would have been too close to each other plus I only had a few left and found they were scratched; they got binned. I used Schaeffer for a quick-turnaround panel; not cheap but very well made. In a moment of madness I got 5 panels made, including engraving (which the original 2 modules didn't have).
ModuleModule CV and gate/trigger translator
This is just a quick post to show what I have been doing with regard to the ModuleModule design I mentioned in my last blog post. More info will unfold over the next weeks but this is just to let several Muffwigglers know that I am progressing their ideas (albeit a bit slowly). These are just a first draft and the design will change. The idea is that there will be a common design that supports either Buchla/Euro or Buchla/Serge; the only difference being the connectors used. It's difficult fitting all I want in the smaller ModuleModule format - perhaps the trim pots will come out and I'll add scale switches as per the CVGT1 - your feedback would be valuable!
CV2 - a sister module for the CVGT1
This is another idea I've been mulling over which will complement the CVGT1 and is intended for non-pitch critical CVs and for audio level translation. Again it's just a preliminary idea and feedback is welcomed.
2012 for various reasons has been for me a real struggle and so am hoping 2013 will turn out to be a better year. My wish on this first day of 2013 is that it will be a very happy and healthy year for you and your loved ones.
2012 saw just a few successes:-
The second was the development, prototyping (including two custom built modules) and preproduction run of the CVGT1 Euro Buchla translator module which are now delivered to the pre-order list customers who are putting them to good use.
Related to the CVGT1 was my first foray into surface-mount boards - the preproduction run of 30 CVGT1 modules used through-hole components which meant that I could, and did, hand build those modules. However they were so time consuming to build that I got quotes for getting them made but the cost was was prohibitive; I was advised that surface mount assembly would be much cheaper and so I set about relaying the boards for surface mounted components. This worked well and they worked first time albeit for the most significant financial commitment I have made in Synovatron to date.
CV Tools may get the same reworking but will keep the through-hole version in existance for you DIY enthusiasts; the CV Tools DIY Kit has continued to be a succesful product with more plaudits about the kit presentation, clear instructions and ease of build.
The downside for 2012:-
Following a personal loss in July I took some time out and then I pushed very hard in the last 2-3 months to produce a large batch of CV Tools and CVGT1 modules for the end of 2012 but due to supplier quality issues it now looks like those modules will not ship to distributors until late January to early February.
I had to reject two thirds of CVGT1 front panels due to scratches and had to reject a batch of 1000 jack sockets due to varying quality from stiff to non-functional (i.e. can't insert a patch lead); unfortunately many were assembled on boards before I discovered this. So all in all a huge amount of effort and frustration with no output but I have learned lessons from this. 3.5mm connector quality is certainly the hardest component problem that Eurorack manufacturers seem to face followed closely by front panel quality issues.
Another problem encountered but Eurorack users is the ease of misconnecting the power cable.
This was brought sharply into focus by a client who reverse connected his RS-35 using one of my ASM2DB Adaptors and blew up the tantalum capacitors and a CA3046 IC on the RS-35; notably all the TL072 ICs survived as did the F-V converter chip.
The connection instructions are clear but we are human and our capacity to f**k up goes with the territory (hence the disclaimer in the instructions); I still do it even though I know to be careful. I have fixed his module for free as a goodwill gesture but it does worry me - my plea to all designers of new modules is use protection diodes.
