#and swapping in my midi controller/keyboard+pads

[sarasa-cat]

Hm. Readjusting placement of things on my computer desk for better ergonomics and ability to SEE my monitors without eye strain and discomfort when working on my graphics tablet as primary view/workspace.

And now I need to rework all the wiring.

But not today.

I suspect this whole week will be a game of micro adjustments.

[taperwolf]

Thrift store find, and a project:

Got this Alesis QX25 MIDI controller in as-is condition for $12. The most obvious problems when I got it were that the fader cap and one rotary encoder knob were missing, and one of the black keys was broken. In addition, there were solfege stickers on the keys, implying the previous owner was pretty young; that impression was backed up when I opened it to find maybe half a container of assorted glitter inside.

The fader cap I haven't come up with yet, and I've put a temporary knob on the encoder — the one at the far right — and I was able to partially disassemble the keybed and glue the key back together. (I'm using Gorilla Glue's superglue formulation, which is supposed to be better than usual cyanoacrylates at bonding plastics; if this doesn't hold, I know where to order replacements.) From a quick once over, the current status is that some of the tact switches are broken somehow — the ones, at least, for octave up and transpose down don't work. I've only given those the most cursory inspection, so I don't know if it's the switches themselves or something in the wiring; I'll have to see if my big box of tact switches has anything I can swap in for them.

But the "project" part is the part that has me enthused. Unlike a lot of more recent MIDI controllers, this one has both a USB jack for connecting to a computer and a 5-pin DIN jack for traditional MIDI instruments. It's also got a lot of spare room inside the case. So I'm looking at taking an Arduino or a Teensy and some little digital-to-analog converters and adding the ability to output CV and gate signals for modular synthesizers. Basically the Arduino will listen to the MIDI signal and interpret that; the minimal feature set is a single note off channel 1, just the CV and gate corresponding to the most recently struck key, but may expand to multiple notes and/or handling the drum pads as their own gate/trigger outs, and probably an extra CV out that can follow the mod wheel or pitch bend.

I'm debating which DACs to use. I have some lying around — the spoils of a time when Linear, Analog Devices, and Maxim were separate companies, and they, Microchip, and Texas Instruments would give out free samples if you had a plausible-sounding company name — but a lot of them aren't particularly well-suited for this. I want to run everything off the existing 5V supply — either a wall wart or USB — and not need elaborate external analog circuits to do things. I'm looking at the MCP4811, a single-channel 10-bit device, which has the advantage of an internal voltage reference at 2.048V, and a ×2 output, for a full range of 0V-4.096V that's very reliable even when run off a unreliable 5V power supply, like the keyboard's USB power input.

(In an ideal world, I'd have a perfect 1v reference, and a precision adder, so that the full precision of the part, all the bits, could be applied to just the 0-1V range, and then I could add single volts as needed to specify the octave. If we're calling 0V C0, then with the 10-bit setup over the 4.096V spread, you have to use value 396 to get G1, and you're imperceptibly sharp; with ten bits over a single volt, you'd use value 597 and add an extra volt and you'd be... slightly closer but flat this time. So the ideal world can fuck itself, and I'll see how the thing I actually have works.)