Distortion Meter and Audio Interconnect Tester

In this article for audioxpress, Ed Simon writes: "There seems to be controversy over what testing means in audio. Measuring a difference does not mean you can hear it. On the other hand, if my ears tell me there is a difference between two audio chains and I cannot measure it, that does not mean it is not there. Probably, I'm just using the wrong method to determine audio differences." And after trying to measure all sorts of things to compare which ones sounded fine - or not - he decided the next step would be to build a dedicated more sensitive measurement. This article was originally published in audioXpress, November 2009.

This project is a great suggestion for a new affordable high-end 2 x 40 W Class D audio amplifier implemented with a Hardware Attached on Top (HAT) board to connect onto a Raspberry Pi Zero platform, creating a solution ideally suited for DIY audio projects. On the other hand, this is a very clever way to promote the Merus amplifiers from Infineon and get a great number of developers and enthusiasts to actual use it, get to know it, and understand its advantages in a real audio project. This article was originally published in audioXpress, January 2020.

This approach to RIAA equalization results in a high-quality phono preamp featuring the high-transconductance 5842 tubes. The author adapts Erno Borbely's project of a transistorized phono preamp with a vacuum tube implementation. These articles were originally published in audioXpress, October 2003 and January 2010. For this repost, we decided to merge the two articles in one single page.

In this project for audioXpress magazine, Jan Didden offers a modern update on his original 2014 high-voltage delay design, which he built to complement tube amplifiers. The new unit needs no additional outside power, and allows setting the delay between 20 seconds and 254 seconds, which should cover all requirements. The article describes the complete project, and there's a DIY kit available at diyaudio.com. This article was originally published in audioXpress, November 2019.

For this review, Ken Bird details his experience in building a set of speakers from Swans Speakers Kits, part of a new catalog created by HiVi Acoustics and Swan Speakers (HiVi's consumer brand), and that so far includes two kits: a two-way bookshelf design, the DIY 2.2A, and the slightly larger three-way design, the DIY 3.1A, the model sent to audioXpress. Both models incorporate HiVi drivers. This article was originally published in audioXpress, August 2019.

Longtime audioXpress contributor Gary Galo writes about a transformer-coupled balanced output circuit for solid-state preamps, usable with line-level signals. Exploring the differences between balanced interfaces and unbalanced interfaces - and finding things that we really want to be aware of, he then explains why he selected Jensen transformers for his own project. This article was originally published in AudioXpress, February 2019.

Now, what's a Null Tester? The Null Tester sends the same audio signal through two paths, then it electronically subtracts one signal from the other to obtain the difference. For years, many audiophiles and even some audio professionals have believed that signal wires can sound different. Obsessed with settling this dilemma, Winer designed a Null Tester device that compares any two signal wires and reveals their difference to a level below -110 dB. This article was originally published in audioXpress, June 2019.

I completed the design and construction of an archival phono preamplifier, which provides variable equalization along with several other operational necessities for playing vintage records (78-rpm discs, pre-RIAA LPs, lacquer transcription discs, and so on). When it came to selecting topologies for the balanced inputs and outputs, I ruled out transformers due to high cost, physical bulk, and weight. The most practical choice, in terms of size and cost, are the balanced line driver and receiver ICs made by THAT Corporation. This article was originally published in audioXpress, June 2010

In this project article for audioXpress, George Ntanavaras describes the design and construction of a high-quality RIAA preamplifier for moving coil cartridges based on high-quality Analog Device AD797 op-amps designed for low-noise audio applications and driven from very low source impedance. This article was originally published in audioxpress, March 2014.

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.