A Low-Mu Triode Preamp

In this article, originally published in audioXpress, February 2004, the author describes how to achieve low distortion from power triodes. As he explains, his preamp is “a little different from most, using low-mu power triodes to get good performance with only one amplifier stage, and no negative feedback. This achieves the modest gain required along with very low output impedance.”

The Glass Audio Special edition is a tradition we have retained since the former title was merged with other magazines to become audioXpress. audioXpress still publishes tube-related articles, but we feel this is one of the highlights for our readers and it certainly is among our authors due to the amount of articles we receive — increasingly addressing applications outside of the typical high-end living-room stereos.

Attention, all first-time (or wanna be) builders of single ended directly heated triode amps. This project’s for you. This is an easy to build, simple direct-coupled input/driver circuit that provides the proper drive voltage to the grid of the 211. A nice way to experiment with a single-ended (SE) triode amplifier.

Member Name: Shannon Parks Location: Mahomet, IL An audio engineer at his own company, Parks Audio, Shannon Parks is proud to have almost all the Audio Amateur magazines in his library and he has been reading audioXpress for quite sometime. Shannon owns Parks Audio and is the administrator of the DIYtube forums (www.diytube.com).

Location: Forlì, Italy Education: Electronic Engineering, University of Bologna, Italy Occupation: Fabio is a lean production and audio expert for a big international company. He also has two small Italian audio brands and a very small top-quality vinyl label. Member …