This page is to detail my ideas for a ‘single-function’ 4U modular synth format. It may be interesting to view the threads on Muff Wigglers forum which have discussed this in the past to see how I have ended up with these specifications, links here:
thread I started recently discussing the idea
(there are a lot of older threads started by other DIYers. but I can’t find the links at the mo, will update when I find them! Needless to say, this is not my own idea, but comes from a “group discussion” as it were!)
By single function I mean entirely modular, neither full or half panels like Serge, nor only a couple of fixed widths like Buchla. My plan is that each module (VCO, VCA, LFO etc) can be made individually and have it’s own panel which will enable the classic swappability of other modular formats (euro, MOTM, Frac etc).
My original idea was to create a format to complement other 4U projects, specifically the Best Of CGS (Zthee) and COA modular (Dmitri) panels which have become central to my studio since building them. In this sense I thought the idea would work best if there was somehow a way to continue adding to my synth using the same sub-cases (Hammond or Bud enclosures, 7” high, 17” wide) which I have in my cabinets, whilst at the same time enabling the use of euro rack rails with tapped strips or vector rail (sliding nuts) mounting into other bespoke cases, or indeed just screwing them into cheaper DIY cases with wooden rails.
I experimented with fitting vector rails into budboxes, and this works very well (but an update to this procedure is coming, the old info was rather out of date I’m afraid!) I have therefore placed the module mounting holes in suitable places vertically to fit this system (see further details on this below). Horizontally I have used a 1” spacing of mounting holes to line up with euro rails (mounting holes at 1HP increments = 5.08mm or 1/5”)
In fact the mounting holes and module widths are based on Doepfers euro rack specifications (more info can be seen on their website - link at bottom of page) the main difference I envisage (apart from the 4U height obviously) is that all modules are only divisible by whole inches.
All panels are actually 175mm high (rather than 7”) this is to allow for a bit of tolerance and to fit into a budbox neatly - again the measurement is in mm for us Europeans… The extra 1mm each end also allows for the lips on eurorack rails, making a total of 177mm (4U).
Here is an example panel (2 UMW - Unit Module Width to differentiate from the ‘HP’ of euro rack) showing dimensions etc, everything should in fact be rather self explanatory!
There are obviously many other specifications for a modular format, such as power supply, signal levels, gate/CV range, cable type etc. It goes without saying that I would recommend bananas (4mm sockets)… The power supply is not particularly important to me as such, I have both 15V and 12V systems, and enough equipment to not worry about signal matching. If I’m making something new I tend to go for 12v and the Serge signal standards and banana colouring. Generally, unless a module absolutely requires 15V (or needs many mods to work on 12V) everything is run at 12V. For power I recommend either Doepfer’s PSU2 or a suitable Power-One or similar dual-linear supply.
NEXT STEPS
I’m now in the process of trialling the final panel designs, and and will then work on offering a group buy situation for panels (in all likelihood on Muffs or e-m), which will then be available through me on this blog. I have toyed with formica panels, and these are a possibility (see through blog for and idea of how these look) but I think that the ‘classic’ aluminium panel is more than likely what I will be offering.
These are the latest panels I have on order, and show the aesthetic I am heading for:
HOW TO MODIFY A BUD OR HAMMOND CASE:
More new info to come soon!
Addendum
Doepfer Mechanical Details: