nickca

1. Pots. I ordered some nice 10K ones from Mouser, originally I had some incredibly cheap ones that worked horribly. I forget the brand, it wasn't a super well-known one like Bourns. I have an encoder for the left/right datawheel, though. Actually, I sort of have a question about that: the encoder really doesn't work that well. It "jumps" and sometimes goes in the opposite direction. Is that just a software thing? I've tried two different encoders, and the latest is a high quality Alps. 2. I had to cut traces for the LEDs. The breakouts are for a diode-matrix configuration, and the Midibox needs 16 individual buttons and LEDs. For the buttons, there are vias you can solder to directly, and for the LEDs I just cut the traces and soldered to the LED's anode directly. Edit: The case is a PacTec PT-10, the same as the x0xb0x and others. The only thing about it is the faceplate is aluminum, and sort of difficult to machine. There's no way I could have cut 16 individual squares for the buttons: I used one of SparkFun's bezels, cut a big square hole for it, and mounted it to the faceplate with a combination of screws and JB Weld (a brand of "metal epoxy", dunno if it's known outside the USA)

My Midibox64 Description and a picture are in the link. If anyone would like info on how I modified the SparkFun button pad, I can provide it. It's quite simple, the two traces for each button have vias you can solder to, and anyone with reasonable electronics knowledge should be able to figure out what traces to cut for the LEDs. The worn/old aesthetic is intentional. I purposely gave the faceplate one coat of flat black spraypaint so it would easily scratch. I was sort of going for a "salvaged and repurposed 1960s Soviet submarine control panel" look. Edit: "Midibox Newbie" as a title is kind of funny. I built my first Midibox64 in like 2003, and I think this is the third Midibox forum I've posted on.

Hi, I've built a small, minimum MBFM without a control surface. I've gathered that I can edit patches with JSynthLib, but how do I perform the more complex actions such as routing different patches to their own audio outs? How do I use the drum mode? Are there SysEx messages or something? Is it even possible, or should I just build a full control surface? Thanks in advance.

Well, you could eliminate the imbalance by running the +/- voltages through positive and negative 9v regulators. If I understand correctly, the opamps just need a bipolar supply, not necessarily +/-12v. I actually was going to do that originally, but it worked without them so I omitted them to save space. As for PSU noise, I haven't noticed any.

Hi, I've just completed my Midibox FM, and I have a working solution to the -12v problem that I don't think anyone's tried yet. My MBFM is totally minimal: no control surface, just a core, OPL3 board and bankstick. I happened to have an old laptop power supply that provides seperate, nicely regulated 5v and 12v, and I'm using it to power my MBFM. If your power supply only provides 12v and you have the full control surface, this might not work due to the additional load, but if you have a full control surface and can obtain a power supply like mine, it should work fine since all the extra load will be on the 5v. Anyway, here's the trick: I used this circuit: 555 Timer negative voltage generator to invert the 12v to a little over -11v, which is fine for opamp purposes. There are many variations of this circuit floating around, I just used this one because I happened to have the parts in my junk box. Every different variation uses different resistor/capacitor variations, but they all work the same way: the 555 converts the DC to an AC wave, and the capacitor/diode network rectifies it to negative DC. The reason I say it might not work with a full control surface and a single 12v supply is the negative voltage decreases (gets closer to 0v) as you add load. Since the load in my minimal MBFM is, well, minimal, I get an output of pretty close to -12v. It works perfectly, and fits on a tiny scrap of perfboard. Much simpler and safer than mucking about with transformers. If anyone else wants to give this a try, I'd be interested to hear how it works in an MBFM with a full control surface and a single 12VDC supply. It may still work fine, but with the LCD and LEDs, there's a lot of extra current being drawn, so I don't know. It's worth a shot anyway, it takes maybe 10 minutes to wire together out of less than a few bucks' worth of parts. Also, I used a CMOS 555 and 1N4148 signal diodes since it's what I had lying around. If you use an original NE555 and 1N400x (say, 1N4003) diodes, supposedly you'll get less voltage loss.