You Can DIY!: Repurposing an Old Preamp for Line-Level Duty

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.

In this article for audioXpress, Bill Reeve helps us to make sense of a misunderstood circuit. A capacitance multiplier is useful as a power supply low-pass filter. It is commonly said that, like Miller capacitance, the capacitor’s value in this circuit is “multiplied” by the transistor gain (β) to lower the filter’s pole frequency. The transistor-enhanced filter does that and more, as the article explains in detail. This article, an excellent tutorial on analog circuit design, was originally published in audioXpress, August 2012.

In this article, Bill Reeve explains how to drive tube heaters with a constant current to lengthen the life of your vacuum tubes. As he explains, obviously, the best way to extend your amplifier’s vacuum tube life is to never turn it on. Some would say that the second best thing you can do is to never turn it off. The third and fourth options may be to gently turn on the tube heaters and not leave the B+ voltage on when the heater voltages are off. This article was originally published in audioXpress, May 2014.

In this article for audioXpress, Bill Reeve discusses “An Alternative to Linear Regulators.” A project were he searches for equivalent power-line ripple rejection with less power dissipation, using a source follower-based (SFB) low-pass filter. Because no one wants to listen to an audio amplifier that hums. This article was originally published in audioXpress, April 2014.

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.

Bill Reeve’s article, “Repurposing Antique Radios as Tube Amplifiers,” provides vintage radio resources, simple circuit diagrams, and essential part info. He also covers the topics of external audio mixing and audio switching. The article appeared in the May 2012 edition of audioXpress magazine.