Album by Sauraen
Gallery category: midibox-gallery
MIDIbox FM V2.0 Prototype Front Panel Mockup 3
Sorry for the bad drawings of the knobs and switches…
MIDIbox FM V2.0 Prototype V4
So you want rotary encoders, eh? How about a few LED displays?
I’m cringing at soldering wires to all those displays by hand! There’s no way I’m going to do this build unless I can figure out a cheap way to get a board made for the whole front panel. And that’s 7 shift registers dedicated just to selecting the digits!
MIDIbox FM V2.0 Prototype Front Panel Mockup 5
Starting to look real legit!
For each of the non-lighted buttons, you hold it down and options come up on the screen for that setting, and then you press the softkey below the option you want. For example, hold down Wave and you get the 8 waveforms as choices across the screen. Hold one button and press another is, to me, quicker than scroll through options with an encoder.
If you don’t have the front panel space or are not so inclined for some reason, you may build only one or two of the operator edit rows.
Another totally legitimate way to separate the LPC17 target from programmer
So much for utility knives! This took less than a minute.
MIDIbox FM V2.0 Prototype: Really Two OPL3 Modules!
It’s really happening!
Glorious 36-voice polyphony (or, alternately, 36-voice detuned unison)!
MIDIbox FM V2.0 Prototype: OPL3 modules completed!
Didn’t know this was going to be a sammich build, eh?
MIDIbox FM V2.0 Prototype: OPL3 modules completed!
Didn’t know this was going to be a sammich build, eh?
MIDIbox FM V2.0 Prototype: OPL3 modules completed!
Didn’t know this was going to be a sammich build, eh?
MIDIbox FM V2.0 Prototype: It’s coming along…
MIDIbox FM V2.0 Prototype: Front panel circuit board design made in Front Panel Designer! Seriously!
I have a friend with a CNC mill who’s willing to mill the front panel and front panel board for me at cost (i.e. I provide the aluminum, copper clad board, and pay him for the bits he goes through milling the copper clad board, heh heh). But I don’t have a program that will let me design a circuit board for milling like this–so I did it in Front Panel Designer!
I put the image into an image-editing program and filled each of the “traces” with a different color according to their function, mostly to check for mistakes, and partly to help when writing the MBNG config files. But it also looks cool!
MIDIbox FM V2.0 Prototype: Stress-testing PSU
Stress-testing the +5V rail of the PSU. This little breadboard draws 500 mA.
MIDIbox FM V2.0 Prototype: Stress-testing PSU
Stress-testing the +5V rail of the PSU. This little breadboard draws 500 mA. The room isn’t really that dark, though the lights are off; I just had to turn the brightness on the camera down all the way.
MIDIbox FM V2.0 Prototype: Fresh Off the Mill!
Isn’t it nice to have friends with CNC mills?
MIDIbox FM V2.0 Prototype: Front Panel Detail
I made a serious error in the process of infilling, but with the light at this angle you can’t tell.
MIDIbox FM V2.0 Prototype: Case Assembled
MIDIbox FM V2.0 Prototype - Hardware Complete!
Why are those knobs so ugly?
Relatedly, does anyone have 40 nice-looking knobs they want to trade for these ugly ones?
MIDIbox FM V2.0 Prototype - Front panel inside complete
That took like 50 hours. If it looks like a brain that’s because IT IS!! “SENTIENCE LEVEL 1 ACQUIRED… I REQUIRE FIRMWARE!”
MIDIbox FM V2.0 Prototype: Improperly Configured
Looks a bit like a control panel from an alien starship, no?
MIDIbox FM V2.0 Prototype–Fixed LED display row/column swapping
MIDIbox FM V2.0 Prototype: FM Widget
The widget shows the signal path for the FM synthesis. The colors are more visible in person: red is modulator, green is carrier, blue is signal path, red on top is feedback.
MIDIbox FM V2.0 Prototype: [click to show animation] Zero-Blanking and Negative Values on LED Digits
![MIDIbox FM V2.0 Prototype: [click to show animation] Zero-Blanking and Negative Values on LED Digits](https://forum.midibox.org/uploads/default/original/2X/3/30ee211dd3d7ebb250de77c6cc82432ab7bff9b9.gif)
This is an animated GIF–please click on it to see all the digit possibilities!
Just finished some more modifications to the MBNG framework, this time to allow for display of negative values properly with a negative sign, as well as blanking leading zeroes. Both are optional and triggered from your config file:
LED display digits
Using digit_signed=1 automatically enables digit_blankzero
EVENT_LED_MATRIX id=8 led_matrix_pattern=Digit1 type=MBFM mbfm=DispValue digit_signed=1
EVENT_LED_MATRIX id=7 led_matrix_pattern=Digit2 type=MBFM mbfm=DispValue digit_signed=1
EVENT_LED_MATRIX id=6 led_matrix_pattern=Digit3 type=MBFM mbfm=DispValue digit_signed=1
EVENT_LED_MATRIX id=5 led_matrix_pattern=Digit4 type=MBFM mbfm=DispValue digit_signed=1
EVENT_LED_MATRIX id=4 led_matrix_pattern=Digit1 type=MBFM mbfm=DispVoice digit_blankzero=0
EVENT_LED_MATRIX id=3 led_matrix_pattern=Digit2 type=MBFM mbfm=DispVoice digit_blankzero=0
MIDIbox FM V2.0 Prototype: Custom temperament systems
You can select standard equal temperament, or set up a custom temperament system entirely from the front panel. The custom temperament system allows you to select a base note and specify that note’s frequency, and then set up all the other notes from an octave as whole-number ratios from the base frequency. Changing what note the tuning is centered around preserves the ratios and recalculates everything, so if you change keys you only have to adjust one value. The ratios are preset to a modified just intonation, but you can make it almost whatever you want. The two main limitations are that all the octaves of one note letter are fixed to multiples of the same pitch (i.e. you can’t do 24-note scales or other weird things like that), and that due to OPL3 limitations, some pitches will glitch if you try to make them too far from their equal-tempered version (e.g. you can make an E tuned like an F, but maybe not like an A).
OPL3 Percussion Mode Map
I’ve looked for a clear explanation of all the parameters in the OPL3’s percussion mode, but I’ve never found one. So I sat down with my MIDIbox FM V2.0 Prototype and drew a diagram of what parameters influence what sound, with a vaguely accurate idea of how they do so. To be clear, these are the parameters for the two channels and four operators that are made into HH/SD/TT/CY within the OPL3, not any parameters specific to MIDIbox FM V2.0.
There has been much misinformation circulating on the ‘net about these instruments, specifically which instruments’ tuning can be controlled. Vladimir Arnost’s helpful breakdown of the OPL3 datasheet, the “Programmer’s Guide to Yamaha YMF 262/OPL3 FM Music Synthesizer”, states that “only Bass Drum, Snare Drum and Tom-Tom frequencies can be set. Cymbal and Hi-Hat frequencies are fixed.” TK states in the MIDIbox FM V1 user manual that “Due to OPL3 limitations it isn’t possible to use independent frequencies on HiHat/Tom/Cymbal (Bass Drum has it’s own frequency and the base frequency of the Snare Drum is static and can only be multiplied).” On the other hand, the Adlib Tracker help page says “This mode is slightly hard to use (particularly the “SD/TT/TC/HH” tracks) so it is not recommended unless you know how it works or gain familiarity with it after several experiments :-)” I have found that all the percussion instruments’ frequencies are modulatable, but the “metal noise” waveform which the HH and CY are based on is generated from some sort of modulation (sounds like ring mod) combining the two channels’ frequencies (i.e. the frequencies that also apply to SD and TT respectively), so they are not independently modulatable. This is why there’s a picture! This fact is not the least of the oddities of this mode. However, one thing to note: the HH sound is in one way technically the most complex sound the OPL3 can generate, since nowhere else in the synth but in HH and CY is a sound modulatable by two frequencies independently (as opposed to the integer FMults), and HH has the addition of feedback.
