A High Performance Microphone Preamp

This article by Ron Tipton details the design and construction of the TDL Model 401 high-performance microphone preamp, using a differential input stage that used compound transistor pairs with circuit resistance values, computer optimized for very low output noise. This is a great example of Ron Tipton's TDL Technology projects, which he managed from his home base in Las Cruces, New Mexico. Sadly, the audioXpress community lost one of its most esteemed and prolific writers. There's no better way to pay tribute to Ron than revisit some of these projects. This article was originally published in audioXpress, October 2002.

This simple single-ended amp project by Pete Millett is a great performer and a very well documented project that was immediately adopted by many DIY'er's. The amplifier achieves good power output and low distortion by employing “E-linear” feedback in the output stage. This article was published in audioXpress, April 2005.

In this great article, author Are Waagbø, himself a confessed "a passionate 50-year-old hi-fi amateur, with many years of practice and experience," and admirer of Erno Borberly work and designs, shares his experience in the relentless search for "the ultimate audio voltage regulator." As Waagbø writes, "Testing more shunt models with selected components and numerous listening tests led to one current-source-fed super shunt, developed by Erno. I developed the PSU, which, together with the sophisticated shunt, sets a new standard for audio voltage regulators." This article was originally published in audioXpress, February 2008.

Following the publication of its original SE 6C33C amplifier in audioXpress July 2004, Ari Polisois returned with more information on how to further simplify the whole construction and reduce the costs. The results, as the author describes, "combine the advantage(s) of the push-pull (mainly power) to the wonderful character of the SE: sensitivity, smoothness, simplicity, and warmth (due to the 2nd harmonic content, easily tolerated by our ears, as against the third, fifth, seventh, and so on harmonics produced by the push-pull)." This article was originally published in audioXpress, February 2008.

This article from respected author Ari Polisois deals with a single-ended amplifier with enough power to drive even the most difficult speaker systems - delivering 50W per channel. This is a project that quickly became the focus in lots of tube-oriented forums and has inspired long threads and many iterations, including further articles published in audioXpress from the author himself. This article was published in audioXpress, July 2004.

"A good tutorial on interfacing microphones to soundcards." This was the brief description preceding Paul Loewenstein's article in the original edition of audioXpress. We think that's more to it. The author describes a microphone amplifier designed to interface a standard dynamic microphone to a soundcard or other computer microphone input with a 5V through 2.2kΩ bias to the microphone connector ring. This article was originally published in audioXpress, February 2008.

In this article, Joel Hatch explains how to build a variable frequency synchronous motor controller to control turntable speed. Now that turntables are back in force, this excellent project not only allows some knowledge about a vital part of the motor's rotational speed adjustment, but it also dives into one of the most crucial aspects of a record player for anyone interested in a little DIY or restoration projects. This article was originally published in audioXpress, December 2010.

In this article, Ron Tipton explores the use of stroboscope discs to determine whether your turntable is set to the correct rotational speed. Apart from looking at some commercially available stroboscope discs, Ron Tipton explains how to print one from files that are freely available on the Internet, and explains how to build your own multiple-LED lamp to check the rotations. This article was originally published in audioXpress, December 2010.

A popular hybrid amp design available for headphone use, this single-ended (SE) pure Class-A amplifier is capable of driving headphones between 32 and 600Ω, and was derived from an original tube/MOSFET line amplifier project, published by Erno Borbely in Glass Audio (1/98). Originally published in audioXpress in April 2005, this project was meanwhile extensively discussed in multiple DIY audio forums all over the world and is probably one of the most tested of Erno Borbely's designs, with multiple iterations frequently published on blogs and other publications.

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