You can DIY! The F5 Power Amplifier

In 2008, Nelson Pass submitted an article on its new F5 power amplifier design to audioXpress. At the time, he wrote: “I feel that it’s important to support AudioXpress, a magazine with which I have a 35 year history, and which also serves as a mainstay for the DIY community. Lately they have kindly printed projects that I had already posted on the web, but I decided that they deserve a little better than that.” Effectively, the F5 project was published in May 2008 and had a huge impact on the global DIY community and certainly contributed for the fact that audioXpress is still around today.

Stuart Yaniger wrote a great article for audioXpress in February 2009, The ImPasse Preamplifier, describing a tube preamp to drive a pair of Nelson Pass’ First Watt F4’s (or other low-to-unity-gain power amplifiers) in balanced mono. Yaniger’s preamp is truly an elegant design with very, very low distortion, using a 6SN7 to drive a 6922 in balanced mode. There are LED’s, NE2H neon lamps and depletion MOSFETs in the design.

Over the years, some of the best Nelson Pass projects have been featured by Audio Amateur and audioXpress magazines. The A40 power amp article was published in The Audio Amateur, 4/78, and the A75 power amplifier appears in The Audio Amateur 4/92 and 1/93. His other works are posted at passdiy.com. Originally published by audioXpress on May 2010.