A Prototyping System for Passive Crossovers

Speed up your crossover prototyping and preserve your crossover components with this true plug-and-play approach. As the author, Ramkumar Ramaswamy explains, today’s computer simulation software allows you to design passive crossovers extremely accurately. “Is there a way to effortlessly and reliably plug and play with a set of (fixed) capacitors across crossover prototypes without the fear of ending up with broken leads? This question drove me to design this passive crossover prototyping system”, he explains. This article was originally published in audioXpress, March 2007.

One of the most important speaker building projects published by audioXpress, THOR was designed by Joseph (Joe) D'Appolito, who is world-renowned for his pioneering work on MTM-based (mid-tweeter-mid) loudspeaker configurations. The original THOR transmission-line design was published in May 2002. For this online publication, audioXpress kept the original article unchanged, which has since been updated with availability of the original Madisound/SEAS kit and the publication of a complete kit project on the SEAS website. Read the complete article here.

In 2008, Nelson Pass submitted an article on its new F5 power amplifier design to audioXpress. At the time, he wrote: “I feel that it’s important to support AudioXpress, a magazine with which I have a 35 year history, and which also serves as a mainstay for the DIY community. Lately they have kindly printed projects that I had already posted on the web, but I decided that they deserve a little better than that.” Effectively, the F5 project was published in May 2008 and had a huge impact on the global DIY community and certainly contributed for the fact that audioXpress is still around today.

Many articles have appeared regarding projects using one of the most sturdy, versatile, and trustworthy audio tubes ever made — the 6550. Most of them show these audio beauties used in the push-pull configuration in order to obtain the greatest efficiency and the most power output. In this article, the 6550 is used in a clean, sweet-sounding, single-ended design. The amplifier has very few parts, is easy to build and repair, and the cost of the project is nominal when you consider the kind of sound that is produced. This article was originally published in audioXPress, September 2001.

In the February 2015 issue of audioXpress, Mark Driedger discussed a tube power amplifier controller based on the Arduino open-source microcontroller. In this follow-up article, Mark Driedger explains how to use some of the Arduino’s untapped capabilities to incorporate the bias meter into the amplifier controller with virtually no additional hardware. A temperature sensor and over-temperature shut-down capability are also included. This article was originally published in audioXpress, May 2015.

In a nod to the Maker Movement, this project uses a common open-source microcontroller module, the Arduino, to build an automatic power controller for a tube power amplifier. The resulting controller is very simple — a $25 Arduino module, a couple of dual op-amps, a few other components, and a 5-VDC power supply plus some opto-isolated switches. This article was originally published in audioXpress, February 2015.

In 2014, audioXpress invited Scott Dorsey to update his popular reamping project that modeled the source impedances of a couple typical guitar pickups. He wrote the original article more than a decade ago for Recording magazine. In “Reamplification Revisited,” Scott brought us an updated version of his Kludge reamplifier box with added detail. This article was published in audioXpress, January 2015.

Following the publication of the original Hideaway TL Sub project in audioXpress July 2006, Bjørn Johannesen submitted a follow-up of its “invisible” subwoofer project, using a new updated driver - a Peerless 10˝ SLS 830668 woofer - and a slimmer profile to fit under its new couch, with only 15cm of free space. The article was originally published in audioXpress, October 2007.

This article, a Danish blueprint for an “invisible” subwoofer was originally published in audioXpress July 2006 and it is the first of two by Bjorn Johannesen. In this first article, the author describes a successful transmission line to replace a vented sub, inspired by Rick Schultz articles. A project where the first approach revealed a resonance frequency lower than expected — lower than the driver’s Fs, leading him to study Martin J. King’s quarter wave design.

Here is an excellent beginner’s project for those just getting started in this hobby. This “little” amp is easy to construct and has only about 25 parts in each channel. The system transformers are very inexpensive, and the total cost involved for a complete stereo version should be very minimal! This article was originally published in audioXpress, December 2001.