Audio category

“ApplePi DAC” audio HAT

ApplePi DAC Audio HAT Add-on For The Raspberry Pi Features 24-bit DAC And A 128dB SNR

Orchard Audio quickly exceeded its $5K Kickstarter goal for its ApplePi DAC HAT board, which it is promoted as “the most advanced and highest performance sound card hat for the Raspberry Pi.” You can order the add-on board from May 13 starting at $175. Options include a $5 stacking header and a $25 5.25V, 3A power supply. The ApplePi DAC supports the Asus Tinker Board and’s Sparky in addition to the Raspberry Pi.

“ApplePi DAC” audio HAT
“ApplePi DAC” audio HAT

A fully assembled $374 system provides the new HAT board, header, and power supply plus a Raspberry Pi 3 SBC, an acrylic stand, and an SD card with a choice of preconfigured Volumio, Rune Audio, or Raspbian. For $574, you get the assembled system plus a 7-inch touchscreen. All the products ship in July.

The board is powered by dual TI Burr-Brown DACs (PCM1794A) configured in monaural mode. The system has a dynamic range of >135dB and a signal-to-noise ratio (SNR) of 128dB, which can bump up to 132dB. Total Harmonic Distortion + Noise (THD+N) is listed as an impressively low <0.0005% (-106dB). The board supports both 16- and 24-bit bit rates, as well as sample rates of 44.1, 48, 88.2, 96, 176.4, and 192kHz.

Orchard highlights the board’s ultra-low noise linear regulation and low jitter PLL clock generation. The mentioned derives are not from the usual crystal, but rather from a CS2300 IC from Cirrus Logic. This clock chip integrates a crystal, PLL, and clock multiplier into a single device, the input jitter is attenuated by 60dB (1/1000). It is remarkable that the onboard balanced (Mini XLR) and unbalanced (RCA) outputs are driven by dual differential output circuit stages. Orchard says that most competing boards offer only single-ended outputs. So, this feature really makes it stand out.

The ApplePi DAC runs at 4.5W and can be powered by a Raspberry Pi, but the manufacturer recommends using the optional 5V adapter. In addition to Volumio and Rune Audio, the ApplePi DAC supports moOde Audio, piCorePlayer, and Roon Network Endpoint software.

The ApplePi DAC is available on Kickstarter through May 13 starting at $175, with shipments due in July. More information may be found at the ApplePi DAC Kickstarter page and Orchard Audio’s ApplePi DAC product page.

Nui – IR Volume Controller

Alvaro Prieto made an IR volume controller and wrote a post on his blog detailing its assembly:

Nui is an IR controlled volume controller for analog audio. It sits between your audio source and speakers and can amplify or reduce the volume using IR commands (and eventually BLE).
Why do I need this?
It all started because I have my trusty Logitech Z-2300 speakers and subwoofer I purchased back around 2004/5. They still work great, but instead of being on my computer, they are used for my TV. Unfortunately, the TV’s line out doesn’t honor the TV’s volume and is always outputting at max volume. Sure, I can get up and change the volume on the speakers themselves, but wouldn’t it be more convenient to do it with the TV remote?!
That’s how the Nui project started. It sits between my TV and my speakers and now I don’t have to get up to change the volume 😀

Nui – IR Volume Controller – [Link]

MEMS technology shrinks loudspeakers

Miniature MEMS-based speakers could revolutionize speech and music reproduction in mobile communication devices. They combine the advantages of a large frequency bandwidth and high acoustic quality with the ability to generate very high sound levels. Nevertheless, they are so tiny that they can be integrated into headphones. By Christoph Hammerschmidt @

The breakthrough has now been achieved. The characteristics of the chip-based loudspeaker are impressive: With currently a area of 4×4 millimeters, the MEMS loudspeaker can be optimally integrated into headphones, hearables and hearing aids. They cover the entire frequency range from 20 Hz to 20 kHz as a one-way system – comparable HiFi loudspeakers typically consist of woofer, a midrange loudspeaker and a tweeter for the high frequencies. The tiny MEMS speakers achieve a sound pressure level of 110 dB for in-the-ear applications – this corresponds to the noise level of a jet aircraft at a distance of 100 meters.

Low Cost/Voltage 3W Class-D Stereo Audio Amplifier for Portable Gadgets

This low cost low voltage 3W class-D stereo amplifier is based on PAM8403 IC, The PAM8403 is a 3W, class-D audio amplifier. It offers low THD+N, allowing it to achieve high-quality sound reproduction. The new filter-less architecture allows the device to drive the speaker directly, requiring no low-pass output filters, thus saving system cost and PCB area. With the same numbers of external components, the efficiency of the PAM8403 is much better than that of Class-AB cousins. It can extend the battery life, which makes it well-suited for portable applications. Trimmer Potentiometer helps to adjust the volume control, CN1 provided to feed the audio signal, CN2 power supply, Mute and shutdown in, LS1 and LS2 to connect the speaker. Shutdown and Mute pin required high level signal input, and can be connect to VDD power pins for normal operation, can be connect to GND for shutdown or mute the audio. The amplifier works well with standard audio signal input.

Low Cost/Voltage 3W Class-D Stereo Audio Amplifier for Portable Gadgets – [Link]

adafruit feather 328p

Adafruit Feather 328P – Arduino Uno on the Feather Family

Adafruit Feather 328P is the latest addition to the ever-expanding feather family boards manufactured by Adafruit. The Adafruit Feather development boards are a set of development boards made by Adafruit that can either be standalone, stackable or both. The feather boards all includes a LiPo battery connector, which will allow projects to easily be powered by LiPo batteries for on the go use.

Adafruit Feather 328P
Adafruit Feather 328P

The Adafruit Feather 328P is based on the popular Atmega 328P, the same processor that powers most Arduino maker boards especially the legendary Arduino Uno. With the Feather 328P, you can bring classic Arduino Uno code and even libraries to the Feather form factor. Measured at about 51mm x 23mm x 8mm (without the headers soldered in) and it weighs just 4.8g.

The Feather 328P is lightweight and a small form factor development board. At the heart of the Feather 328P is an Atmel ATmega 328P running a 3.3V and 8MHz. At 8MHz, the feather 328P can’t fully compete with the Arduino Uno which runs at 16MHz but is fair enough. The Feather 328P includes a 32KB of flash memory (storage memory), 2KB of RAM, and it uses the SiLabs CP2104 to give it a USB-to-Serial program which also provides users with some integrated debugging capabilities.

feather on a breadboard

The Feather 328P boards come without any headers soldered, so you have to solder yourself to start using it for prototyping. Unlike the Arduino Uno and some other Arduino board which are not fully breadboarding compatible, the Feather 328P fits perfectly into a breadboard and will be great for quick prototyping without the need for jumper cables.

Like other Feather development boards, the Feather 328P also includes a LiPo battery connector for any 3.7V Lithium Polymer batteries with a built-in battery charging. It will charge straight from the micro USB port, and you don’t necessarily need a battery to make it work, it will run just fine straight from the micro USB connector. The Feather will automatically switch over to USB power when it’s available making sure your project never goes offline as far you still got some juice in the battery though. You can also measure the battery voltage through one of the analog pins, the analog pin must not be connected to anything for this to work.

The following are some of the specifications of the Feather 328P:

  • Size  – 2.0″ x 0.9″ x 0.28″ (51mm x 23mm x 8mm)
  • Weight – 4.8 grams
  • Processor – ATmega328p @ 8MHz with 3.3V logic/power
  • Power –
    • 3.3V regulator with 500mA peak current output
    • Built-in 100mA lipoly charger with charging status indicator LED
  • USB serial converter (CP2104) for USB bootloading and serial port debugging
  • GPIO –
    • 19 GPIO pins + 2 analog-in-only pins
    • 6x PWM pins
  • Connectivity –
    • Hardware I2C, SPI.
    • For UART devices, should use SoftwareSerial
  • Others –
    • 8 x analog inputs (two are shared with I2C)
    • Pin #13 red LED for general purpose blinking
    • Two LEDs for serial data RX & TX
    • Power/enable pin
    • 4 mounting holes
    • Reset button

The Feather 328P comes with an extra prototyping area to add some couple of components without using a breadboard. The Feather 328P is available for purchase and priced at $12.50, you can buy now online at Adafruit Store. To find out about the other feather boards, check them out here.

MEMS loudspeaker with extremely small dimensions along with low power consumption and good sound quality.

World’s Smallest MEMS Micro-Loudspeaker Saves 80 Percent More Energy

STMicroelectronics along with the audio company USound has created the first MEMS (Micro ElectroMechnical Systems) micro-loudspeaker based on semiconductors. It’s the smallest loudspeaker in the world, but it can produce a powerful noise. MEMS makes it possible. The speakers are being presented at CES 2018 in Las Vegas.

MEMS loudspeaker with extremely small dimensions along with low power consumption and good sound quality.
MEMS loudspeaker with extremely small dimensions along with low power consumption and good sound quality.

In the audio world, the electromechanical capabilities of MEMS have only been used to build tiny microphones. Speakers, on the other hand, still rely on traditional dynamic design principles. It has taken almost 150 years for semiconductor technology to replace Werner von Siemens’ superior loudspeaker principle in 1877 with something newer. The Coil-magnet combinations are still being used in smartphones, wearables, and headphones to produce sound.

We can understand the working principle of MEMS speaker very briefly here. At first, thin piezoelectric layers are applied to a semiconductor(Silicon). An electric signal is sent to the piezoelectric layer allowing the diaphragm connected to it vibrate. Eventually, the mechanical principle resembles that of a normal Coil-magnet loudspeaker. The sound is created by the vibration in the diaphragm. However, the magnet and coil are replaced by a piezo element. By applying this new technique, USound’s MEMS version appears to offer significant advantages when it comes to distortion and THD or Total Harmonic Distortion.

The MEMS loudspeaker developed by USound has dimensions of just 5 x 7 x 2 mm and has a frequency range of 2 to 15 kHz. It takes up half the space of its predecessors and needs only 20 percent of the energy that they do. The above figures are convincing enough for the speaker to be a perfect fit for mobile applications such as wearables and smartphones.

According to the manufacturer, these tiny speakers are the thinnest in the world. It has less than half the weight of a conventional Coil-magnet speaker. Most suitable applications include in many portable devices such as headphones, over-the-ear earphones, and more. With the help of this new speakers, augmented reality headsets or virtual reality systems can be more compact and comfortable. Innovative features also enable 3D sound production with striking accuracy. Its high efficiency reduces energy consumption and can easily be operated with much smaller and lightweight batteries. Higher efficiency results in less heat generated making systems operate cooler than ever before.

The Little Buddy Talker – Arduino Compatible Speech Chip Set

Small, versatile, fun, and inexpensive! Use the 254 word library to bring speech to your Arduino projects! Speak, Arduino, Speak!

About a year ago, I designed an Arduino shield that allowed for you to add voice to your electronic designs.  I’ve since been able to minimise that design into a much less inexpensive, and smaller unit.  This unit has a 254 word library that consists of colours, commands, months/days/time, numbers, directions, feelings, units of measurement, security words, math lingo, and general words; all of which are spoken by “Lucy” – A lovely female voice with an English accent! Meet “The Little Buddy Talker” Arduino compatible speech kit set!  It is Production Ready, and eager to land in your hands!

The project is live on kickstarter and has 29 days to go.

XMOS VocalFusion- Background Noise Not a Problem Anymore

The XMOS VocalFusion XVF3500 voice processor, to be shown at CES. Source: XMOS


XMOS is one of the many companies that has ventured in voice recognition technology. They created the VocalFusion XVF3500 device, the first voice processor to have true stereo-AEC support in a far-field linear microphone array solution. Voice recognition is a relatively new technology for consumers which we came to know with Siri, google home, Alexa etc. However, this technology has been developed since 1950s with a very limited understanding of numbers. Nowadays, voice recognition software can answer all kind of questions, perform activities (such as calls, notes and web searches), and even answer to sarcastic questions. Experts predict that 50 % of all web searches will be made using voice by 2020.

Voice recognition is not only about not using keyboards, but also about security and usability. Thanks to software such as Siri people can now make phone calls in the car without even looking at their phone, play music and send messages. The biggest problem is accuracy specially when dealing with accents which the voice software may not be able to comprehend.

Speech recognition works by analyzing the sound, filtering what you say and digitalizing it into a form that the computer can read, and then analyzing it for meaning. It has become increasingly complex to program this kind of software because of language, dialects, accents, and phrasing. Also, background noise can easily throw off the interpretation of your speech.

At CES 2018, XMOS plans to display their new XVF3500 voice processor alongside the VocalFusion 4-Mic Dev Kit, which was the first far-field linear array solution to achieve Amazon AVS (Alexa voice service) qualification, delivering easy integration of Amazon Alexa into commercial and industrial electronics. The kit is based on the VocalFusion XVF3000 device which provides acoustic echo cancellation and advanced noise suppression. This will allow developers to build Alexa enabled products which will accelerate it’s deployment in new systems and new devices giving customers the ability to access Alexa from more places.

The development kit includes the XVF3000 voice processor, I2S serial audio and I2C serial control interfaces, cables, xTAG debug adapter and much more. It enables across the room voice interface solutions which are then processed by cloud based recognition software even in places with complex acoustics and noisy environments. This could help solve the background noise issues allowing a more accurate interpretation and an improved user experience.


Hi-Fi Stereo Headphone Amplifier using LME49600

This project is the ideal solution for high output, high performance high fidelity stereo head phone amplifier. The project consists of Op-Amp LME498720 and LME49600 as output driver. The LME49600 is able to drive 32Ω headphones to a dissipation of greater than 500mW at 0.00003% THD+N while operating on ±12V power supply voltages.  The LME49600 is a high performance, low distortion high fidelity 250mA audio buffer. The LME49600 is designed for a wide range of applications and is fully protected through internal current limit and thermal shutdown.

Hi-Fi Stereo Headphone Amplifier using LME49600 – [Link]

Design of a Korg Nutube Amplifier

Karlwoodward @ is in the process of designing a “guitar pedal” for amplification and distortion using the Korg Nutube we featured earlier. The Part 1 of a series of articles goes through the basic aspects of tubes and valves, the pros and cons on using a Nutube valve as well as discussing about low gain and high source impedance. In Part 2 of the series he goes deeper by building a working prototype and making some measurements.