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Tuesday, June 29, 2010

Change in plan

So, the total knee has given me a lot of time to sit and at least try to think. It occurred to me that I really need to consider this project not as a "one-off" system for me. With Nyle's encouragement to share and release this stuff,  I realized (finally...) I need to take a more universal approach to the PCB/panel designs and consider those who are going to stuff just one or two of the modules into an existing Doepfer rack or something. I've been looking at the Doepfer racks and they can be as shallow as 80mm in front of the power supply itself. It looks like the general minimum is about 100mm and I think most modules will fit this form factor. The sequencer as it stands now may be a problem, but since the panel will be so wide, I can rethink it and make it wider, but shallower.

I also decided I'd better put a 10 pin 0.1 inch spaced power header for the true euro rack users. I'm keeping the 4 pin, .156 inch spaced connectors for me and the MOTM/Frac guys. I am seriously considering throwing a 10 volt regulator on each PCB, too. But, that seems like a hack to me somehow. When I get the next set of prototypes built, I'll just test them on +/- 12 and if they work, I'm not going to worry about it. If they don't, I might just have to put the regulators on the PCBs since I doubt many people will dedicate a -10 volt power supply for 1 or 2 modules and I'd really like to see people build these.

So, here's how the plan is changed:

  1. Pick a "standard" size board and keep the depth to less than 100 mm if at all possible (the sequencer and VCO may be a problem). I'll stick to 3.95 inch tall (just under 100 mm euro rack standard) so they will fit vertically in a Blacet rack or euro rack.
  2. I'm not going to do PCB mounted pots but will have headers to facilitate using MTA connectors and flying wires.
  3. I will pick a pot spacing for the panels I design to accommodate a spacing compatible with a knob like the Alco PKE60B1/4 or PKES60B1/4 and an Alpha 16 mm pot. The knobs have a retro look, but are smaller than the original Steiner knobs which will let me shrink the module widths for the EGs and VCOs at least. They aren't much bigger than the soft touch knobs Blacet uses or the Doepfer knobs, but I think they look more in keeping with the original. A spacing of 1" maybe 1.1", for the pots should be good. I know that you can get as close a 0.75 inches on a Frac or Euro panel using smaller knobs, but it's really tight. I don't want to waste space, but I need some room for these chunky fingers of mine. Staying away from PCB mounted pots also gives the user a much wider choice of parts and mounting configurations.
  4. I will need to design a custom module and/or daughter board which will interface the S-Triggers and Voltage Triggers. I'm not going to re-work the Steiner modules for this as they were designed to take advantage of the way S-Triggers can be connected together in an "OR" gate fashion. Some users may not care and will need to use voltage triggers to trigger the EGs, or sequencer. So, I will design and build some boards to do this as separate modules.
  5. I'm going to look into the advantage of just having a 10 volt regulator on board. It takes space and a few more components, but if the modules need it, this may really be the only way to do it efficiently. For my part, if I need -10 volts, I'll just change the Power-One supplies to give me +12 and -10.
  6. Add a Doepfer header to the board for the Euro guys and leave the 4 pin MOTM for the rest of us.

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