Fresh From the Bench: Hypex Nilai500DIY 500W Mono Power Amplifier Kit - A New DIY Benchmark

The Hypex Nilai500DIY 500W Mono Power Amplifier Kit is new DIY benchmark from the company's dedicated DIYClassD brand. The kit is specified to deliver 500W with 1% THD at 4 ohms, improves output noise and idle losses significantly, and comes with a discrete buffer stage and voltage regulators. The article, originally published in July 2023, offers an extensive review with measurements of the full kit, including the PS500 DIY power supply and DIYClassD preamplifier kit.

The first article from audio expert Ethan Winer about Modern PCB Design Practices, gave a general overview of board design using surface-mounted devices (SMDs). The article examines current practices and methods for designing four-layer printed circuit boards using surface mounted components (SMDs), and this second part explains specific strategies and related issues to deal with the design and production of great quality PCBs. This article was originally published in audioXpress, March 2023.

In this two-part series, Ethan Winer examines current practices and methods for designing four-layer printed circuit boards using surface-mounted components (SMDs). A great article for our DIY readers and many developers who often are faced with the need to build and test their projects on a properly designed, prototype printed circuit board. Part 1 presents an overview of the process, while Part 2 he will explain specific strategies. Many related issues will be described along the way.

Most of our readers still remember Tom Perazella’s extraordinary egg speaker project with SB Acoustics Satori drivers, featured in the September, October, and November 2018 issues of audioXpress. Inspired by that design, Metz decided to build his own version, and also explore his own take with an active crossover tri-amp approach using a miniDSP 4x10HD system feeding a dedicated six-channel amplifier using Purifi 425W Class-D units. The new Egg Speaker Amp and System is an inspired take on the original. This article was originally published in audioXpress, July 2022.

Ethan Winer offers his fifth Guitar-Controlled Synthesizer article where he describes how to make two key modules needed by every analog synthesizer: the Voltage Controlled Amplifier (VCA) and Voltage Controlled Filter (VFC). This article explains two different VCA circuits, with a simpler one that works fine for one-off projects where precise unit-to-unit repeatability isn’t needed, and a second circuit similar to the VCA in the original Moog synthesizers. This article was originally published in audioXpress, August 2022.

The three previous articles described circuits that Ethan Winer developed for his current project that uses an electric guitar instead of a keyboard to control an analog synthesizer. This article continues with two pieces needed to process input from an electric guitar: the input section’s preamplifier and noise gate, and the pick detector. The preamp amplifies the weak signal from an electric guitar’s pickup and brings it up to line level for further processing. The noise gate detects when a note is currently playing and when it stops. Of course, the pick detector signals each time a new note is picked.

This third article continues to follow Ethan Winer's fascinating journey of building modules for a Guitar-Controlled Synthesizer. The two previous articles described the core circuits he developed for this project that uses an electric guitar instead of a keyboard to control an analog synthesizer. This article continues with two components that are essential for all analog synthesizers: The Low Frequency Oscillator (LFO) and the Attack Decay Sustain Release (ADSR) envelope generator. Both of these circuits generate voltages that control other modules in the synthesizer. This article was originally published in audioXpress, June 2022

There's a lot of everything in audioXpress October 2022. Starting with a market update on audio for Residential Integration. Next, Jonny McClintock shares The Story of aptX, Gary Galo reviews Sumiko phono cartridges and new 78 rpm stylus, Richard Honeycutt explains RT Measurement, Frans de Wit tackles the design of a DC Power Supply, Ken Bird builds a pair of tower speakers with Oaktron drivers manufactured in the US, and Christopher Paul writes about Triode Common Cathode Stages and its controversies.

This DIY-focused article introduces the Pentriode, a concept to explore the familiar idea of connecting commonly available pentode tubes as triodes, creating a circuit that excels in linearity. The Pentriode is formed by making one simple change to connect the screen grid to the cathode of a cathode follower. The article proposes different possible approaches, including for a mu stage, a design that the author previously wrote about for audioXpress. This article was originally published in audioXpress, May 2022.

This is the second article in a fascinating DIY journey of a guitar-controlled, all-analog synthesizer project that will include multiple stages and modules. Following a Sample & Hold circuit designed to retrieve previous voltages that no longer exist, this article details voltage control and how the playing is converted to voltages and back to frequency.