Build a Digital Audio SPDIF Output for Your Computer, Laptop, Tablet or Phone

Even though today's computers, tablets and smartphones are capable of producing ultra high-quality digital audio, it's left to cheap digital-to-analog converters (DACs) to transform it into sound. Those who listen all day to a low-bitrate MP3 stream on a cheap plastic mono bass-boosted Bluetooth loudspeaker probably don't care, but there are people who are willing to invest time and money in quality audio. A good step in this direction is this USB-to-SPDIF interface that allows our digital sources to connect to high-end AV receivers, stereo amplifiers or stand-alone audio DACs. It even features IR remote control.

In the new book, The State of Hollow State Audio, Richard Honeycutt dives deep into the subject of hollow-state audio. This interview covers his interest in hollow state audio, his background, and the future of vacuum tube technology.

You don't always need a nicely etched professional-looking plated-hole printed circuit board to obtain good results. Soldering components to sturdy wires can get you pretty far as shows this video about building a passive tone and volume control for your amplifier.

Practically any amateur musician will be familiar with the old-fashioned mechanical metronome and its nice ‘double tick’ sound. Here were present an ‘old-school’ electronic equivalent.

The things likely to strike any reader or potential buyer of this book are (1) the extremely long title and (2) the term ‘Hollow State’. Fortunately, the book cover helps to identify the subject at a glance by showing four large vacuum tubes (Br.E. ‘valves’), one of which is in brilliant focus to reveal its shiny glass envelope, internal structure and, importantly, the glowing filaments. The warm glow is also seen in the tubes that are out of focus.

Have you ever wondered what an infrared remote control sounds like? With this small circuit you will be able to find out!

With a smartphone or an MP3 player it’s easy to play audio files, but generally not at room strength or if you can, only in wretched quality. The Card Sound project makes it possible to fill the room with music and have excellent sound reproduction! This lightweight and compact player also stands out for its modest quiescent current consumption and desirable extra features such as I²C and RS-485 control.

This circuit adjusts the gain of (small) input signals such that the amplitude of the output signal is constant over a wide range. The control voltage is obtained from a cascade circuit.

Small single-board computers like the Raspberry Pi are ideal for use as small stand-alone network audio players. With Volumio and other specialized Linux distributions, putting together an audio player is remarkably easy. And as ElektorLabs worker Ton Giesberts shows in this article, you can also use this approach to build a high-end audio player.

Vinyl is back with a vengeance among hi-fi enthusiasts. The sound of vinyl records is something very special and cannot be compared to the sound of digital audio sources. In this article we present a high-end phono preamplifier featuring four special opamps wired in parallel in each channel to achieve extremely low noise. We used this approach earlier in a design published back in 1982, with discrete transistors at that time.