If you have observed quite a number of electronic projects, you must have noticed that different range of frequencies is used, sometimes all in a single project. To assist this requirement, this circuit has been developed. The project entitled ‘Top-Octave Generator’ produces 12 distinct output frequencies. A single circuit produces 12 frequencies and each of them is different? Might sound a lot more complicated. However, the circuit uses only one parameter to serve this variation, which is the supplied input frequency to the chip. The frequency fed to the chip is counted down by an exact integer to form a chromatic scale of 12 notes. It can be thus said the type of octave generator or the output of the generator solely depends on the input frequency. This circuit is digitalized and makes uses of digital counters to produce pulse trains. The ratios of the output to input frequency match up to the tones of the chromatic scale. In musical equipments, the output pulse trains are usually converted into sine waves in the audio amplifier section for desired sound effect.
The basic key parameters of this project are enlisted in points below:
- Input frequency range: – The input to the circuit ranges from 250 kHz to 2.5 MHz in general.
- Input capacitance: – The inherent capacitance of the input terminal is about 5 pF.
- Input pulse width: – It is the minimum width of the input pulse that the IC can accept. And 0.2 µs is the pulse width limit.
- Output pulse rise and fall time: – These parameters represent the output characteristic. In no load condition, 1 µs is typical value.
The core application of this project is in electronic organs, electronic music synthesizers, and other electronic musical devices where the need of multiple range of frequency is needed.
In order to achieve the equal tempered scale effect instead of chromatic scale, use only exact replacement ICs.