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From the Vault: The Borbely Preamp

May 14, 2024 by Erno Borbely

From the Vault: The Borbely Preamp

"Designing a preamp is probably the most challenging engineering task in the audio chain, and many designers have invested a lot of time and effort in it," wrote Erno Borbely in this original 1985 article for the Audio Amateur. "My reason for designing this preamp is quite simple: I wanted to have a top-quality preamp without paying megabucks for a Levinson or Accuphase unit. It is up to you to decide whether or not I have succeeded in achieving the same quality." This article was originally published in The Audio Amateur Issue 4, 1985, and is still frequently referenced.

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Audio Electronics: Testing a Tripath Power Amplifier

August 5, 2020 by Ron Tipton

Audio Electronics: Testing a Tripath Power Amplifier

Our late and much esteemed author, Ron Tipton, shared a fascinating project on testing Class-T or Tripath power amplifiers on the pages of audioXpress. As he characterized, these "small, inexpensive, and power-efficient units," sounded good "but testing them is problematic." The article also discusses the story of Tripath Technology and speculates on the reasons why the Tripath ICs remained popular among the DIY audio community. This article was originally published in audioXpress, March 2014.

R&D Stories: Future Shock. Powersoft Audio’s Amplifier Technologies

June 5, 2019 by Stuart Yaniger

R&D Stories: Future Shock. Powersoft Audio’s Amplifier Technologies

Stuart Yaniger details the amplifier technologies developed and perfected by Powersoft Audio, the Italian company based in Scandicci, Florence. From the introduction of Class-D amplification to the unique company philosophy, Yaniger discusses how Powersoft Audio strived to define the technological edge of its markets rather than follow trends. This article was originally published in audioXpress, August 2014.

A Power Supply Spreadsheet

February 7, 2018 by Paul J. Stamler

A Power Supply Spreadsheet

This article describes a spreadsheet program for designing low-voltage power supplies using common IC three-terminal regulators. The spreadsheets are in standard Excel format, and should work in just about any spreadsheet program. Each file has two main pages: one for use with common variable-output regulator chips, the other for fixed-output devices. This article was published in audioXpress, March 2010.

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A Portable Tube Preamp

December 13, 2017 by Gregory L. Charvat

A Portable Tube Preamp

In this amazing project by Gregory L. Charvat, two pre-amplifiers are used with a battery powered high voltage supply. The high voltage supply works by creating a square wave with a 555 timer. The square wave is fed into a small audio power op-amp. The output of this op-amp is back-fed into the secondary of an audio output transformer, generating high voltage AC 170V at 40 kHz. This signal is rectified, filtered, and regulated in a conventional sense. The entire system runs on 8 AA batteries and should operate for approximately 4 hours continuously. This article was originally published in audioXpress, March 2010.