audioXpress September 2019 Speaker Focus Edition Now Available

The September edition of audioXpress is our always popular Speaker Builder - Speaker Focus edition. Once again, audioXpress focuses on loudspeaker building, design, and testing and for this issue we have combined two great DIY articles with a review of the PureAudioProject Trio15 Heil AMT speaker system. Ward Maas reports from the High End 2019 show in Munich, Jan Didden met with Purifi Audio's Bruno Putzeys and Lars Risbo and comments on the company's research, and much more.

For audioXpress May 2019 -Glass Audio Special - we’ve put together a very strong edition, with some of best tube experts sharing a series of DIY projects for all skill levels, from restoration projects to new amplifiers, preamps, and headphone amps. We review the Nu:Tekt HA-K1 headphone amplifier using the novel Korg Nutube 6P1 device, and interview the founder of Parks Audio. We go deep on measuring voltage regulator ripple rejection and we even look at square-wave testing. All inside audioXpress May 2019!

This article by Ron Tipton details the design and construction of the TDL Model 401 high-performance microphone preamp, using a differential input stage that used compound transistor pairs with circuit resistance values, computer optimized for very low output noise. This is a great example of Ron Tipton's TDL Technology projects, which he managed from his home base in Las Cruces, New Mexico. Sadly, the audioXpress community lost one of its most esteemed and prolific writers. There's no better way to pay tribute to Ron than revisit some of these projects. This article was originally published in audioXpress, October 2002.

In this article, Joel Hatch explains how to build a variable frequency synchronous motor controller to control turntable speed. Now that turntables are back in force, this excellent project not only allows some knowledge about a vital part of the motor's rotational speed adjustment, but it also dives into one of the most crucial aspects of a record player for anyone interested in a little DIY or restoration projects. This article was originally published in audioXpress, December 2010.

Oftentimes a muting circuit for the output of a preamp is left out of DIY applications as an unnecessary or annoying part of the project. This is usually due to the lack of awareness that a simple circuit can perform such a duty. Anyone who occasionally forgets to turn the power amp on last, or switch it off first, endures the annoying thumps and noises that often occur from the preamp upon power cycling. This article proposes a simple circuit for preamp muting. The article was originally published in audioXpress, March 2010.

With many audio manufacturers and consumer electronic companies experimenting development with voice recognition applications, Google naturally wants to make it easy as possible for anyone to get familiarized with the company's Google Assistant SDK, to implement voice interaction. Billy Rutledge, Director of AIY Projects at Google, recently revealed a new voice recognition DIY kit and voice HAT for the Raspberry Pi.

This project is based on a previous audioXpress article: “A Solid-State Single-Ended Power Amp” by Ed Simon, published in the April 2006 issue. Ron Tipton was deeply impressed with this amplifier project which used only five transistors per channel, two of them being current sources. This article was originally published in the old audioXpress website as a PDF, but was never reposted. Now we make available online with updated references and links.

In this simple amplifier project, Ed Simon describes a Class-A amplifier design that mainly intends to reproduce music with reinforced emotional expression. That's what you normally get with a quality design, but to achieve it, the author shares the complete concept, power requirements, circuit topology, construction and testing of this single-ended amp... in a solid-state design. This article was originally published in audioXpress, April 2006.

At the 139th AES convention in New York, Solid State Logic announced the introduction of βeta, a unique 500 format module Hardware Development Kit using SSL specific components. Now audio electronics enthusiasts can build creations that will look as cool as they sound and feature real SSL controls.

Here is a simple portable device from George Ntanavaras that can help answer the question about peak voltage and peak current requirements and whether or not your power amplifier is capable of driving your loudspeaker without clipping. This article was originally published in audioXpress March 2015 — Focus on Test & Measurement Edition. (Updated Dec 2015)