You Can DIY! Type 3 Mu Stage Breakthrough

The original Mu Stage project, published in Glass Audio in 1993, remains a popular build, serving the author's purpose to "combat listener fatigue." His Type 2 Mu Stage, published by audioXpress in 2019, introduced a streamlined version with added capabilities. Now, the new Type 3 Mu Stage resulted in what the author believes to be a breakthrough, improving the realistic reproduction of music. This latest iteration of the circuit was prototyped by Kim Bond, an enthusiastic builder of the previous Mu Stages.

Or why not all grounds are created equal. How to mitigate grounding issues in audio equipment, understanding resistance, inductance, and capacitance of ground wiring, and voltage differences between points. Also, how not add to the construction complexity.

This modification and restoration article shows how to preserve the best features of unused tube equipment. The article describes a tube preamplifier that the author wanted to position at the input to his home power amplifier, eliminating the need to adjust his 1972 McIntosh MX10 tuner and 240 power amplifier’s volume high when he wants to fill his home with music. In this case, an old Shure Model 65 stereo conversion preamplifier using two dual-triode 12AX7 tubes provided an excellent platform for the project. This article was originally published in audioXpress, May 2020.

Our May 2021 Glass Audio Special edition is certain to inform and inspire you. We reveal what is happening at Western Electric's new Rossville Works in Georgia, where production of 300B tubes is ongoing, we explain how to draw tube load lines, and we offer a valuable preamplifier design that enables you to compare the sound of tube and solid-state circuits from the same audio source. There's also a versatile stereo tube amplifier design to build, and plenty more audio electronics theory and practice in this edition. Now available online and in print.

In this article, Mark Driedger revisits “The Remaking of a Champ,” inspired by Kirk Elliott’s original article for Glass Audio (1992). The Fender Champ is considered “the” classic tube practice amplifier and it has been remade a few times over. Driedger created his own version, including a provision to easily try different output tubes. This article was originally published in audioXpress, January 2016.

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!

In this amazing project by Gregory L. Charvat, two pre-amplifiers are used with a battery powered high voltage supply. The high voltage supply works by creating a square wave with a 555 timer. The square wave is fed into a small audio power op-amp. The output of this op-amp is back-fed into the secondary of an audio output transformer, generating high voltage AC 170V at 40 kHz. This signal is rectified, filtered, and regulated in a conventional sense. The entire system runs on 8 AA batteries and should operate for approximately 4 hours continuously. This article was originally published in audioXpress, March 2010.

Antique tube radios are some of the most coveted vintage electronics any audio enthusiast can acquire. They sound absolutely great, both as for what they are intended - to work as a good old analog radio - but also as an amplifier for external audio sources, including any digital source. In this audioXpress article, from May 2012, Bill Reeve shares how to approach such projects and provides excellent advice.

This Class A tube headphone amp project, which the author created for Vintage Audio, includes a 6SL7GT for the input stage and a 6AS7G for the driver, and is able to drive headphones with impedance at or above 64Ω. The article provides a full description of design fundamentals and some useful guidance on the construction process. The result, as the author describes, should be “a satisfying headphone amp that will provide years of enjoyment.” This article was originally published in audioXpress, June 2008.

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.