The Dynaco ST-70 Series 3 Tube Amplifier is Now (Finally!) Shipping

Previewed in 2016, and originally scheduled for Spring 2017, Dynaco (a division of Radial Engineering Ltd.) announced the ST-70 Series 3 tube amplifier is now shipping. Since acquiring the legendary Hafler and Dynaco brands in 2014, Radial Engineering has been carefully working on the Dynaco ST-70 Series 3 tube amplifier, in an effort to create a truly worthy successor of one of the most successful tube amplifiers of all time. The result is finally available!

Peter Delos details how to add tone controls to a three-channel tube-based guitar preamplifier. The circuit is a versatile building block anyone can use for his or her own preamplifier applications. The project is implemented with three 12AX7 gain stages. The tone control at the final output is a standard bass, mid, treble control circuit found in many guitar amplifiers. This article was originally published in audioxpress, October 2014

Tube amplifiers can benefit from regulated and stabilized power supplies, especially sensitive preamplifier stages, but also (single-ended) power amps. But traditional high-voltage regulators add several extra tubes, complexity, and power losses, while good performance is not easy to obtain. This article, published in audioXpress, April 2009, describes a novel design that is very simple yet offers excellent performance. Output voltage is fully adjustable with a single resistor without any compromises in performance.

Keeping things small and inexpensive — and at the beginner’s level — Rick Spencer shows you how to build your own single-ended amp. For about $10 worth of tubes and some small transformers, you can build this neat little amp in one weekend. This article was originally published in audioXpress, April 2004.

In this classical tube amplifier project, author Bob McIntyre offers what is effectively the foundation for many designs that we can find currently in the market. This is not surprising. The Mighty Mouse is indeed a good sounding and inexpensive project that is also a good introduction to tube amplification. This article was originally published in audioXpress, April 2006.

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.

Shannon Becker conducts an interview with Dave Thomson, CEO and founder of Raven Audio, a tube amplifier company based in Texas, which has successfully created a thriving business with high-quality tube amplifiers and preamplifiers. Raven Audio just opened a new facility in Onalaska on Lake Livingston, 100 miles north of Houston, and continues to expand its engineering staff. This article was originally published in audioXpress, June 2017.

Published in two separate parts in audioXpress October and November 2007, this hybrid amp design is a detailed and interesting project, frequently referenced by other DIY audio enthusiasts. We thought it was time to make it available online in its entirety, in the best possible quality. The article discusses the unity-gain, single-ended MOSFET output stage, the valve voltage amplification stage and wraps up with the power supplies, printed circuit boards, and construction.

Magnatone announced a newly redesigned Lyric amplifier as part of the company's Studio Collection. Built in the tradition of the great modest amps of the '50s and '60s, the Studio Collection offers vintage American tones, with improved power and versatility for the modern player. The new Lyric offers fat, honest tone and responsive natural overdrive, with a new larger cabinet and custom-designed 12-inch speaker, the Lyric is as comfortable in the studio as it is on Stage.

Here’s an amp project especially for first-time builders featuring the 6BQ5 tube. As Rick Spencer writes in its introduction, "In order for this beloved hobby of ours to thrive and survive well into the future, we must always strive to make it interesting to newcomers." With this in mind, Rick Spencer created this single-ended design using the 6BQ5/EL84 tube in triode mode. This article was originally published in audioXpress, October 2008.