Open source hardware ESP32-ADF

Here’s an open source hardware development board for Espressif audio development framework, the ESP32-ADF, from Olimex: With ESP32-WROOM-B module with 8MB RAM and 4MB of Flash, two microphones, two 3W speakers, codec, amplifier, Lipo charger, USB with programming, Audio 3.5mm jack, ESP32-ADF board offers everything you need to start playing with Espressif Audio Development Framework. Check […]

App note: Active filtering in automotive audio applications

App note from Texas Instruments on isolating DC and high frequency noise in audio using their automotive op amps. Link here (PDF) Phone calls, emergency alerts, and music are just a few of the reasons that a high quality audio system is vital in automotive infotainment and clusters. Operational amplifiers (op amps) are one of […]

Transistor radio series: the AF power amp

Vasily Ivanenko @ QRPHB writes, “I sought a low distortion, single supply, AF power amplifier for my transistor radios. I’ll present my experiments, some musings, test equipment and a reference to some wonderful books & their wise author. Sadly, some amateur radio receiver builders diligently craft their RF stages, but skimp on the PA audio stage. […]

Arduino controlled Dual Mono AK4490 DAC (part 3)

Here’s the part 3 of Dimitris’ Arduino controlled Dual Mono AK4490 DAC project we covered previously: Following up on Part 2, it’s time to talk about the output stage. This output stage is the brainchild of my friend Kostas, all I did was lay out the PCB. It is a fully discreet single-ended class-A output stage, […]

App note: BH45F0031 Earphone jack communication

Holtek’s App note about their audio to digital signal converter chip BH45F0031 that together with an phone app, communication via audio phone jack is possible. Link here (PDF) The BH45F0031 is a Flash type 8-bit high performance RISC architecture microcontroller, which is designed for smart phone headset interface applications that can directly transmit data and […]

App note: Class D audio amplifier basics

Class D audio amplifier an efficient amplifier by Infineon Technologies, Link here A Class D audio amplifier is basically a switching amplifier or PWM amplifier. There are a number of different classes of amplifiers. This application note takes a look at the definitions for the main classifications.

App note: Measuring a loudspeaker impedance profile using the AD5933

An application note from Analog Devices about AD5933, this provides a low cost substitute to expensive test equipment like signal generators, oscilloscope and voltmeters in getting the speaker’s impedance profile. Link here (PDF) This application note describes a circuit architecture using the AD5933 that allows the system designer to measure the impedance profile of the […]

App note: The 2-Channel serial audio interface: A tutorial

A pretty older application note about the serial audio interface by Cirrus Logic. Link here (PDF) It may come as a surprise to those trying to make their initial investigation into audio systems design that there is a de-facto standard for transferring audio data within a system. Despite the differing naming conventions used within the […]

App note: The LM4935 headset and push-button detection guide

Another headset plug-in detection from Texas Instruments. Link here (PDF) The headset detect circuitry can differentiate between mono, stereo, mono with microphone, and stereo with microphone headsets. It can operate while the LM4935 is placed into low current standby mode, which promotes extended battery life. In standby mode, it consumes no extra current, if the […]

App note: WM9712 Jack plug auto-detection, hookswitch detection and microphone headset detection

App note on Cirrus Logic’s WM9712 jack plug auto-detection by monitoring the connected headphone resistance. Link here (PDF) This application note describes two operations associated with using headset. The first is the facility to automatically switch between a mono ear speaker and stereo headphones for use in a Smartphone, PDA etc. The second operation is […]

flip-flop/BCF project

Ray over at the diyAudio forum has been working on his flip-flop/BCF project: I’ve just finished a project to roll up the developments into a more ‘finished’ build, feeding the balanced outputs from the flip-flop board into a Broskie BCF buffer stage. I’m using Nicks MJ Statistical Regulator for the B+ and one of Andrew’s indirect filament […]

Replacement LED driver for AN6877

Dilshan Jayakody writes: AN6877 is linear AF level meter IC produced by Panasonic and it is commonly found on many audio equipment. This chip is no longer manufactured by Panasonic and finding replacement chip for AN6877 is also quiet difficult. The circuit described in this article is design to replace AN6877 base LED drivers and it […]