Dilshan R Jayakody’s Web Log

Pink noise is an essential tool in audio testing, widely used for analyzing speaker systems, room acoustics, and crossover networks. Unlike white noise, which has equal energy across all frequencies, pink noise features equal energy per octave, making it ideal for audio response testing. This characteristic ensures that pink noise offers a flat frequency response when analyzed on a logarithmic scale, providing a more accurate representation of audio systems. Assembled pink noise generator kit. We developed a this pink noise generator to meet various audio testing requirements. This device combines simplicity and performance, featuring a minimal component count for ease of assembly without compromising accuracy and usability. This pink noise generator design uses a reverse-biased emitter-base junction of a 2SC945 transistor as the noise source. In this configuration, the transistor behaves like a noisy zener diode, producing a broad spectrum of white noise. In this design the NJM...

This project is about a single-channel microphone echo generator circuit. This circuit builds around the Holtek HT8970 echo effect generator IC. It offers complete control of the echo effect by providing delay, mix, and output level adjustments.  HT8970 is an echo/surround sound effect generator IC with 20Kb SRAM. It also contains the built-in VCO stage, AD, and DA converters. The chip costs less than 0.5 US$ and is commonly available in the market. Prototype build of the echo effect generator circuit. The given schematic offers a maximum of 320ms time delay and works with a single-rail 9V DC power supply.  In addition to the HT8970 integrated circuit, this circuit uses an NJM4558 op-amp to amplify the input and output audio signals. HT7150 voltage regulator uses in this design to power up the HT8970 IC. The HT7150 is a low-power 5V regulator IC from Holtek, the same maker of the HT8970 IC. Top view of the prototype build. The circuit designs to work with 500Ω dynamic mic...