You Can DIY!: Revisiting The Remaking of a Champ

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 audio enthusiasts looking for a good read, showcasing some wonderful examples of hi-fi product design and craftsmanship, Mark Driedger suggests taking a look at Gideon Schwartz’s new large-format book. "Hi-Fi – The History of High End Audio Design" is an 8.5” × 11” hardcover “coffee table book,” featuring 272 heavy glossy pages of text and nicely produced photographs. This article was originally published in audioXpress, June 2020.

Accurately setting the bias level for push-pull output stages is important to maximize amplifier performance and tube life. This circuit measures error relative to the target bias current and error relative to a balanced condition in the push-pull pair. The meter is compact, low-cost, simple, and accurate thanks to the use of a window comparator IC - a Linear Technology LTC1042. This article was originally published in audioXpress, July 2012.

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.