Free Electronic Circuit Design
Introduction: PWM (Pulse-Width Modulation) for Digital Audio Conversion Pulse width modulation (PWM) technique has been widely used for converting digital audio stream into audio signal since it is very simple and easy to implement. Many low-cost micro controllers include dedicated PWM controllers as their standards, and many engineers use it for many purposes. In this article, we present the solution […]
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To get various characteristic of an auto wah/quack effect, we need a flexible control of the envelope detection characteristic. Some playing styles need slow attack but fast decay, but some others don’t. Employing the envelope detector circuit presented in our previous article [Ref 1], but with some modification to make it single supply operation. Here we present the improvement of […]
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Introduction to Envelope Detector Circuit Envelope detector circuit is used to get the amplitude profile of a signal. Some important properties of an envelope detector are attack or rise time and decay or release time. In the Figure 1, a signal is plotted in blue, and the detected envelope is plotted in black. Since it employs capacitor for filtering inside […]
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Introduction to Automatic Wah/Quack Effect Automatic wah/quack effect gives a similar effect with the manual version (reference [1]), but without the need of any pedal to manually control the frequency/tonal sweep. This automation is made possible by detecting the envelope signal of the instruments audio signal, and use it to control the filter to produce center frequency sweep, producing audio […]
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A type of guitar effect pedal that produce “wah”- or “quack”-like sound, which is similar to the crying sound of a baby is called wah-wah pedal, or just wah pedal. The effect is produced by filtering the musical instrument through a band-pass filter, which the center of its peak frequency is swept from low to high, mimicking audio tonal transition […]
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Introduction: What is Fold-Back Distortion? I was introduced to a term of “fold-back distortion” in the past by an article from an old book which I forget what the title is, but the book contains schematic diagrams of many circuits collected from old publication of Elektor magazine (www.elektor.com). The article presents the circuit’s schematic diagram and how it works. I […]
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Using some active and passive components, we can build a simple audio-controlled disco light controller circuit. A standard audio power amplifier output, which usually drive loudspeaker, can used to drive this disco light circuit. With this circuit we don’t need light jockey anymore, because the flashing of the light will be directly controlled by the music signal itself. The schematic […]
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The microphone pre-amplifier circuit described here make the microphone sensitive to a sound come from very close source, and insensitive to any sound coming from far sources. This works even when the far sound is very loud. The main application of this circuit is in telecommunication system like in mobile phones, where the microphone should pick a clear speech even […]
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Introduction to Automatic Disco Light Control Simple audio or music controlled disco light uses comparator to sense the beat of a music signal, but this comparator has a reference point that should be calibrated according to the music signal volume. It’s easy if we have a light jockey to take the duty of controlling all the lighting, but it’s not […]
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Sometimes we need small power amplifier circuit while we have unused op-amp section in one of our applied chip. Instead of adding more IC (such as LM386 or similar devices), adding two small transistor and several passive components can be cheaper solution if we can employ the unused op-amp section. Using two small transistors (2N3904 and 2N3906), we can build […]
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For some simple applications such as toys, intercom, or small gadgets, there is sometimes a need for small, simple, low cost, or low voltage solution of power amplifier circuit. For this requirement, high fidelity is rarely needed. A modification of amplifier circuit from Bowden’s circuit collection is presented in our article, completed with the guidance on how to modify for […]
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Basic alarm with small transistors presented in our previous alarm circuit article is usually enough for toys, but we might need more power if we wanna use it for automotive or industrial application. If you usually see class-c amplifier application in radio frequency circuit, then we will show you how it can be applied in audio circuit as well. From […]
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