Organ Sound Generator

Posted on Aug 30, 2012

Originally, the prime harmonics were generated with 74HC4046 PLLs which were spot-on accurate but would take some time to reach their final frequencies, especially when running at low frequencies. They also limited the useful frequency output range and I decided to dump them in favour of not quite spot-on divided-down frequencies. It occurred to me that with a limited number of gears and teeth on the Hammond tonewheel generator, this might be authentic anyway. You can tell that the harmonics are not quite locked by looking at the output signal on an oscilloscope. The principle of operation of a tonewheel organ is to have a fundamental output frequency for each note to which you can add upper and lower harmonics in varying amounts. This device uses a high frequency square wave oscillator which is divided down to provide the fundamental and even harmonics in square wave form. The fundamental is nominally 0.5kHz. The prime numbered harmonics are approximated by dividing down from the H.F. clock with programmable dividers.

Click here to download the full size of the above Circuit.

The frequencies are thus not exact but are very close. The remaining harmonics can be generated by using dividers from the prime numbered harmonics. Note that because of this, the "prime numbered" harmonics are not necessarily really prime, but often multiples of them to facilitate this dividing method. e.g. the tenth harmonic is generated from a divider, and the 5th harmonic is then obtained with a simple flip-flop divider from the 10th harmonic. These square-wave outputs need to be filtered to obtain sine waves. Switched capacitor low-pass filters are used to do this. The clock inputs of the filters are driven from one of the high-frequency divider outputs of the VCO. The particular divider output used is chosen based on getting the corner frequency close to the fundamental of the particular signal being filtered without causing too much attenuation. As the filter corner frequency changes with the clock inputs, the filters will track the input signal and maintain a constant output level and filtering relationship. The sine wave outputs generated can be added together as desired using front panel level controls, in a similar way to that possible using the drawbars on a tonewheel organ. The front panel controls also have voltage control inputs for each harmonic, allowing harmonic levels to be varied by an ADSR unit, or some other control voltage source. The vibrato unit in the original A-100 organ is based on a...

Leave Comment

characters left:

New Circuits

Zero consumption Anti-theft High power Code Switch for E-Bike Batteries

This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
Ultrasonic distance finder circuit

The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Simple Metal detector circuit with CD4030

Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Fully automatic watering circuit for flower pots

Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
Simple deep searching metal detector circuit

The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
Sub-Harmonic Bass Converter for Electric Guitars

The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
Echo Depth Sounding Sonar for Boats

In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
100W HiFi Audio Amplifier Circuit

This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
Plant-Pot Water Level Indicator Circuit

A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....

Create NOW your QR MENU for your Restaurant / Hotel / Bar / Caffe,

Comprehensive ordering/paying features. fully personalized to suit your Business.

Update Anytime! Easy and Simple!

Popular Circuits

200W Lamp Flasher with 555 timer

200W Lamp Flasher is used to flash lamps, bulbs and halogen lamp to give your product that...

Mains Supply Failure Alarm

Whenever AC mains supply fails, this circuit alerts you by sounding an alarm. It also provides a...

avr Control 5V buzzer using mcu and a single 5 V power supply

A PB-12N23PW-05Q buzzer and I`m trying to use it with ATmega 162. I can`t connect it directly to...

modular burglar alarm

This circuit features automatic Exit and Entry delays and a timed Bell Cut-off. It has provision...

Light Related

Watch the video given below to get a better idea on how LED works A light emitting diode (LED) is...