The earliest strobe tuners had used neon lamps to illuminate the strobe disk.
The power supply section is very simple, it consists of a rectifier/filter and a pair of voltage regulators, providing +12V and +3.3V for all the circuitry. The microcontroller will be clocked from a 12MHz crystal, to function as an accurate frequency reference. 2 ADC channels for potentiometer readout It has lots of peripherals, out of which we need: Three pushbuttons will complete the UI part, allowing us to implement some menus in a simple, up/down/select fashion.Īs the brains of the project, STM32F103C8 is just what the doctor ordered: It's fast (72MHz, 32 bit) so it will easily churn out the exact tone frequencies. Another potentiometer will be used to control pitch offset in cents. We're going to need some controls for pitch being tuned - I chose a potentiometer, which will be read with STM32's ADC. To make things even better, lots of excellent libraries have been written for it, it takes 3.3V logic and power - same as STM32s, and Chinese sellers offer ready-made modules with built-in backlight LEDs for very good prices on eBay. Hacker community popularized the PCD8544 LCDs as a cheap, readable display, perfect where HD44780 LCDs are just too limited, and small size is a nice benefit. Having settled on the motor and LED controlling circuits, we need to add some form of user interface. Then, a simple LED modulated by incoming sound of matching pitch should make a pattern appear still. Instead of measuring the tone, we generate it very precisely (simple in electronics world) and use it to spin a motor with a striped pattern. So what is that million dollar idea? The principle resembles setting the ignition on older cars, or adjusting the speed of a turntable. They are expensive, made by sigle company (Once Conn, now Peterson), eager to refresh its patents and capitalize on the same old idea over and over. Invented around 1950 they haven't been outclassed by any modern method so far.
Also: They DO work in the presence of other noises. The response is real-time and the accuracy reaches below one-tenth of a cent. They are the titans of the tuner industry: There ain't a tuning job a strobe tuner cannot do. The bars do not resonate that long, especially in overtones. Still the basic drawback of spectrum analysis remains: To find a frequency to 0.1Hz you have to count the pulses for 10+ seconds. Yet another way would be measuring the frequency electronically. This makes it impossible to view the readout instantly. It might really work, but when it comes to sub-Hz intervals, analysing the spectrum in very narrow intervals requires a sound sample of significant length.
This had to be ruled out, as my ears can only detect a couple of cents of a difference - not really enough!Īnother method is spectrum analysis.
#Musical strobe tuner generator#
The first method of tuning is to do so by ear, comparing the sound from some software generator and from the bar itself. A specific interval, or frequency ratio, between the modes has to be preserved for the piece of vibrating metal to sound like a vibraphone! This topic has well been documented by the marimba builders, who shape the bars out of rosewood. The bar has to be ground down in specific places to alter the frequencies of the modes. Vibe bars are commonly tuned in the fundamental and first two overtones. Another thing is the bars vibrate in multiple modes: the fundamental, lowest frequency mode determines the perceived pitch, and the higher modes are responsible for the overtones which shape the timbre of the sound. The reason is the process must be very accurate (definitely sub-1Hz) for the instrument to sound good.
#Musical strobe tuner full#
Two bars were missing, but I believed that while it might be too hard to make a full set, making just two might actually be possible.Īfter some research I found the main difficulty in making a bar is definitely its tuning. Then, by a blind stroke of luck, I found a set of vibraphone bars quite cheaply available on line. Nothing that cannot be made out of wood, aluminium bars or pipes. An instrument like that consists of a frame, aluminium bars or "keys" and pipes called resonators. The reason behind it is very simple: The cost of a complete instrument is prohibitive, and used vibraphones are seldom available - if ever. A long time ago, me and my girlfriend (a percussionist) decided we want to build a vibraphone.
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