Tag Archives: Audio

Ultrastable UHF transmitter – A super Tiny Radio Transmitter

Dire situations require unpleasant solutions, an excellent example of this statement is spying and we have seen what the NSA has done in this regard. It goes against proper ethical character, however, it might be needed in certain circumstances. Usually, the first thing a person who wants to spy would do would be to check and closely monitor the internet presence or life of the party being suspected and possibly try to access their profile(s). You could also buy an expensive bug or listening device, plant it somewhere the person goes every day, this could be the person’s house and start eavesdropping.

Another method could be to hire a private investigator or a detective to monitor the person’s actions. However, if they are suspicions, you would probably want to do things discreetly. Going the professional route might work, but is also expensive and somewhat not fun to do (less of learning involved). Do It Yourself (DIY) is the talk of the day, why don’t we go that route? And it’s not like this will be the first time someone is doing that, I once did a project sometime ago that can eavesdrop conversation from a person behind a wall.

TomTechTod released an open source radio transmitter, which measures 5mm by 9mm and is powered by a small battery which has a 4.8mm diameter. This device is actually the smallest radio transmitter I have heard of, and it is super tiny, yet this 433 megahertz (Mhz) transmitter has a high-frequency oscillator and a low-frequency amplifier to ensure maximum efficiency no matter the condition.

Other features include the microphone, the battery holder, two transistors, a resonator too. There is also an antenna with a wire and a resistor. The board is 0.8m thick and can transmit up to 120 meters even with obstacles in the area.

One great advantage that comes with going for a super tiny board such as this one is that the PCBs are not expensive thereby making the board super cheap. The boards are being sold for just 45 cents each.

Files needed to create your own transmitter can be found here, with just a bit of soldering here and there, you have your very own spy bug. A super tiny one to be precise. Of course, I am not encouraging you to start spying on everyone you see I am just saying you should go and have fun.

ESP32-LyraT – An Open Source Development Board For Smart Audio Applications

Espressif systems has been working on different audio applications including smart speakers. Despite the fact that they have been developing their audio applications, as of February 2018, none of ESP32 software development kits was easily accessible and the hardware kits were not able to take on any new tasks. So, there were no chances to improve or implement new things using the hardware kits. Therefore, it was not surprising when the company released ESP32-LyraT.

ESP32-LyraT

ESP32-LyraT is an open-source development board, supporting Espressif Systems’ ADF (ESP-ADF Audio Development Framework), one-key Wi-Fi configuration, a wake-up button, voice wake-up, voice recognition, cloud platform access, and an audio player.

The goal was to improve the audio applications of the kits being produced, and this was achieved through ESP32-LyraT, the only board released by Espressif Systems with adequate documentationESP32-LyraT has different voice commands and interactive voice functions; it allows the fast development of applications relating to consumer electronics, wearables, smart speakers, smart home applications and automation. The board facilitates the quick and easy development of dual-mode (Bluetooth + Wi-Fi) audio solutions.

The block diagram below presents main components of the ESP32-LyraT and interconnections between components.

Esp32-LyraT Block Diagram

Features of ESP32-LyraT include UART, USB Power Port, a battery charger chip, an audio codec chip; a sound card which is built in the motherboard for providing sound output. There is also a PA chip, a JTAG header, and UART header. Other parts include the two keys which are the function keys and the boot keys. ESP32-LyraT has a micro SD slot available, a green and a red LED and an ESP32 WROVER Module.

Below are some of the device specifications:

  • Wireless module – ESP32-WROVER module with WiFi and Bluetooth LE
  • Audio –
    • Many audio inputs – Wi-Fi, BT-audio, DLNA, 3.5mm audio Line-in
    • 3.5mm headphone jack
    • 2x microphones
    • Speaker connectors
  • Storage – micro SD slot
  • Debugging – JTGA header, USB UART
  • Misc  – Touch sense buttons, function/boot/reset keys,  DIP switch for configuration
  • Power – 5V via micro USB port; battery header + charger chip

Some Key Featuers

  • SoftAP and Station mode.
  • Various mainstream, both lossy and lossless, compressed audio formats, including M4A, AAC, FLAC, OGG, OPUS, MP3, etc.
  • Two microphones for the development of near-field and far-field voice recognition applications.
  • BLE network configuration, and smart network configuration with apps, such as WeChat.

The ESP32-LyraT board is available for purchase and is being sold for just 22 Euros on Olimex. More information about the product can be found here, and the ESP32-LyraT User Guide is available for download here.

Open Source Ethernet Audio Broadcaster

Luca Pascarella @ open-electronics.org presents how to setup their open source ethernet broadcaster. He writes:

Recently, we have presented an Ethernet audio streaming unit. In particular, we have shown how to configure the boards to work with other similar devices or with VLC Media Player, setting up a point-to-point or a broadcast streaming in all possible configurations. Also in the first episode, we analyzed the electrical circuit and the components choice. Now it is time to describe the board software advanced options and how to update firmware via Internet or manually.

Open Source Ethernet Audio Broadcaster – [Link]

Digital UV-meter with OLED Display

@ instructables.com build a nice VU meter using Arduino and an OLED display.

Hello, instructable. Today I will tell you how to make a simple digital VU meter (sound level meter) using Arduino and OLED displays and 2 resistors by yourself (DIY). The device is quite simple, for beginners it will be a rewarding experience.

Digital UV-meter with OLED Display – [Link]

PiSound – Audio Card For Raspberry Pi

by blokas.io:

pisound is an ultra-low latency high-quality soundcard and MIDI interface specially designed for Raspberry Pi pocket computers. Equipped with 192kHz 24-bit Stereo Input and Output driven by the legendary Burr-Brown chips, DIN-5 MIDI Input and Output ports, user-customizable button and bundled software tools, this little board will bring your audio projects to a whole new level!

PiSound – Audio Card For Raspberry Pi – [Link]

SoundDuino 3, The Latest Sound Shield for Arduino

c51db665a6d43406669fe6369ca97877_originalThe electronics engineer and microcontroller programmer expert, Masih Vahida has launched his latest SoundDuino Arduino shield product: SoundDuino 3!

SoundDuino is a WAV Sound Player & Recorder Shield for Arduino. This sound shield let you record and play sound files to or from a Micro-SD memory card with all libraries and samples for the Arduino IDE.

“SoundDuino is a sound recorder and player that is able to play the sound files from the Micro-SD memory card or even record sounds to the memory with your desired file name. It supports FAT16 and FAT32 and you can easily copy your files into the memory and to play them, you only need to use the library that we give you with this shield and just send the file name that you want to play! Yes, very very easy!” Vahida explains.

This video shows the very first version of SoundDuino and some of its applications

The newest shield, SoundDuino3,  is based on NXP LPC2103 ARM7 32bit microcontroller and it can play 16 bit 48khz sound files with a very high quality. It also has audio input and output jacks, an onboard microphone as well and can work from 3.3v to 5v. SoundDuino fits nicely on an Arduino Uno and is compatible with any Arduino boards using pins GND, VCC, RX and TX. Moreover, the device is delivered with libraries and examples for Arduino IDE.

This project is now live on Kickstarter, check the campaign video

You can use this shield to announce numbers and add you own files into the memory. You can also extend the example code and have it read the text also.

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SoundDuino 3 specifications:

  • Updated firmware, high quality audio
  • Automatic baudrate detection
  • Sound quality is Stereo 16 bit 48hkz (SoundDuino 1 was Mono 8 bit 48khz)
  • Super easy to use, new functions in library to announce the numbers .
  • More useful functions in the library
  • the sound quality is much much better than the last version
  • Small size
  • System voltage is 3.3v compatible with Arduino boards

With SoundDuino shield it seems easier to start building some great audio projects. You can follow the project updates and order your own SoundDuino 3 for $59 now from the crowdfunding campaign.

The SilentSwitcher, A Quiet Mains-free Power Supply

Audio projects become smaller over time with the rapid advancement of technology. A traditional power supply is still considered large compared to audio projects size constraints and it may not fit such delicate applications that need to deliver a good sound with zero noise.

Jan Didden, audio specialist who is known for his own publications Linear Audio, has came up with a new idea that can help in perfecting audio projects. The SilentSwitcher is a 55 x 31 mm special power supply module designed to supply clean power to high-end analog and digital audio circuits.

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“One goal of this power supply that it doesn’t need to connect to the mains, you can use it with a USB charger or with a power bank… All problems with ground loops and mains born noise are not existing”- Jan Didden, the designer of The SilentSwitcher

The SilentSwitcher uses a combination of switching and linear regulators to generate a stable and noise-free supply voltage. The module can be powered from a 5V USB adapter, or from a 5V power bank for complete isolation. It delivers ±150 mA and a choice of 6V, 5V or 3.3V at 0.5 A to benefit most of your applications. The absolute maximum input voltage is 12VDC but in normal operation it is preferable to limit it to 10VDC.

Output specifications:

  • Outputs (analog): +15 and -15 VDC at 150mA* each;
  • Output (6/5/3.3V): selectable 6, 5 or 3.3 VDC at 0.5A*;
  • Output noise (6/5/3.3V): less than 1mV broadband
  • Output impedance (analog): less than 10mΩ (+15V) and 80mΩ (-15V) at 20kHz
  • Output impedance (6/5/3.3V): less than 3mV drop with 100mA current step.

15V output at 150mA are provided thanks to the very low noise linear regulators of Texas Instruments TPS7A47, TPS7A33 that suppress all the noise from the switching regulator by a factor of one thousand even at 1 Megahertz. Such chips have driven zero noise to switcher technology and have shown incredible quiet and low noise performance.

Jan Didden talking about his product

The well designed board will help in keeping all elements quiet and avoiding excess radiation. There are 2- and 3-pin headers on the PCB to connect the load, and a 2-pin header for an On/Off switch. The connection to the 5V source is through a B-type USB connector or a standard 2-pin screw-type connector block. You can mount the PCB on the back of your enclosure with a hole cut out for the USB-B – no further input wiring required.

The SilentSwitcher Connections
The SilentSwitcher Connections

This power supply will be a great companion for your project! No need to think about wiring or transformers, and you won’t face any issues like mains hum or mains earth loops.

The SilentSwitcher is live on a Kickstarter crowdfunding campaign and there are only few hours left to go! You can get your own SilentSwitcher for $59 and you will receive a fully assembled and tested board.

More details are provided at the campaign page and at Linear Audio website.

How to Build a Class-D Power Amp

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Cezar Chirila @ allaboutcircuits.com shows how to build a Class-D amplifier which has amazing efficiency.

What is a Class-D audio power amplifier? The answer could be just a sentence long: It is a switching amplifier. But in order to fully understand how one works, I need to teach you all its nooks and crannies.

How to Build a Class-D Power Amp – [Link]

3W Stereo Audio Amplifier using TDA7266D

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Tiny stereo audio amplifier board has been designed around SMD TDA7266D IC from ST. The TDA7266D is a dual bridge amplifier specially designed for Portable Audio, LCD TV/Monitor, PC Motherboard, and TV applications. This circuit provides high quality audio output of 3W approx. on each channel with standard audio signal input. The circuit works with 3.5V to 5V. Due to low supply input this amplifier is suitable for small size audio gadgets and portable audio applications like MP3 player, Voice messaging system, Warning signals, Annunciator etc.

Specifications

  • Supply voltage range 3.5 to 5v (maximum supply 5v due to small pcb and small thermal area)
  • Output power 3+3w @thd = 10%, rl = 8ω, vcc = 3.7v (3w approx.)
  • Single supply
  • Minimum external components no svr capacitor no bootstrap no boucherot cells internally fixed gain
  • Mute functions (jumper close)
  • Short circuit protection
  • Thermal overload protection

3W Stereo Audio Amplifier using TDA7266D – [Link]

An S/PDIF Sound Card Using PCM2906

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joesugar @ ceworkbench.wordpress.com has designed a S/PDIF Sound Card using the PCM2906 IC.

In the belief that I’d rather build than buy I decided to update one of my previous projects, a PCM2904 based sound card, to include an S/PDIF interface. The update was a cinch because TI has a pin-for-pin replacement for the PCM2904 (the PCM2906) with an S/PDIF interface. All I had to do was replace the audio jacks with fiber-optic transmitter/receivers connected to the appropriate pins.

An S/PDIF Sound Card Using PCM2906 – [Link]