Thursday, March 2, 2017


I'm on show schedule again. Non-profit theater that does free morning performances at local grade schools. So that means a different school every Tuesday and Thursday, show up at 7:30 AM, unload the van, set up the gear, one hour show with no intermission, then break it all down again.

This was the setup as of Tuesday. Today I patched in four more channels of wireless microphone. Which needed a second mixer as submixer. See, that's the thing about these small boards. It may say "16 channels" but what that means is 8 or less mic-level inputs, then the rest of the channels are line level and shared in pairs.

Some mixers take this even further (looking at you, Behringer). Digital input channels are counted, "tape" inputs (RCA jacks that patch directly to the main bus with no trim or EQ) are counted. They even count channels that share controls, meaning you can use "5 and 6" or "7 and 8" -- just not both at the same time.

Well, it didn't go well. There were massive RF issues. Drop-out as well as interference. Some of that may have been the environment (different school every show, and not enough time to do a scan of the RF environment or adjust frequencies). But some of that may have been IM; intermodulation interference between the microphones themselves. So I'm running Shure's wonderful freeware program Wireless Workbench before the next performance to see if it can identify any intermods and find me new frequencies.

This has also been a week for progress on the violin.

Here it is being all tacticool with the clip-on Snark tuner, new shoulder rest, and new (black) carbon-fibre bow.

Anyhow, had a neuromuscular breakthrough; stumbled upon the right mental signal to do the proper arm vibrato gesture. Only for a second, but that was enough to find it again, and again, until I could find it reliably. Soon I'll be able to practice it and start refining it until it becomes instinctual. At the moment, though, it is still a ton of concentration to hit that exact gesture.

There's nothing exactly "vibrating" about the Holocrons. Aside from the "talking" one -- I got fairly decent results clamping a surface transducer against the outer shell and using the Holocron itself as a speaker cone.

There is PWM, of course. Unlike my other LED projects, I'm not using my hand-rolled software PWM library, or the on-chip hardware PWM the multiple internal timers of the AVR series makes possible. Instead the Holocrons are leveraging the WS2812 chip, a chip that combines stand-alone PWM, a constant-current limiter, and serial bus. The "neopixel" sold from Adafruit combines that chip with an RGB LED. More costly at a couple of bucks each, but really makes wiring simpler. All you need is a single signal lead and a 5V source. And they are free-running, which means your code can be busy doing other tasks while the LEDs work away in the background.

(My Holocron code is calling them about 500x a second, though; a slow dim up and down, and superimposed on that, an even slower color shift from blue-red to blue-green and back again).

Anyhow, I'm finally over the 'flu, show is open, so I'm hoping to start shipping within the next few days.

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