All items in category Project Articles
Extend the useful life of those precious tubes: use a Tube Amplifier High-Voltage Delay
by Jan Didden

Extend the useful life of those precious tubes: use a Tube Amplifier High-Voltage Delay

Tube life can be extended if you delay the application of high voltage until after the heaters have warmed up and current can flow. This little module does just that: depending on the setting of a jumper, it delays the high-voltage for 40 or 60 seconds after the amplifier is switched on. And the module is available as a kit. This article was originally published in audioXpress, February 2014.
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The Willow Pre-amp: A high slew-rate JFET amplifier
by Robert Nance Dee

The Willow Pre-amp: A high slew-rate JFET amplifier

This project, originally published by audioXpress in December 2011, has been the topic of much discussion, updates and follow-up projects, so much so that we decided to make it available online. As the author, Robert Nance Dee, explains, “…the people who have listened to this amp can hear the difference. I built it as a companion to my 5002 power amp, both using the HA5002 buffer.”
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An inexpensive, easy-to-build sound level control
by J.R. Laughlin

An inexpensive, easy-to-build sound level control

This circuit contains an audio amplifier capable of driving a speaker with circuitry that automatically maintains the same relative maximum output regardless of extreme levels that are occurring at the input. It does not “compress” the peaks, but simply “turns down the volume” as you would do with your volume control
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FryKleaner: an Audio Burn-in Generator
by Jim Hagerman

FryKleaner: an Audio Burn-in Generator

In this very popular article published by audioXpress in March 2004, Jim Hagerman explains the design theory behind this popular low-cost DIY kit. The FryKleaner was designed to be a complete self-contained burn-in system. Included on the deceptively small circuit board is a very sophisticated waveform generator and built-in power amplifiers capable of directly driving cables. A wall-wart supplies power.
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Build a Passive Surround-Sound Decoder
by Doug Ford

Build a Passive Surround-Sound Decoder

This article by Doug Ford describes a design for a (relatively) simple passive-matrix surround-sound decoder and the interesting things discovered by the author during the process. The decoder features an analog time delay, implemented with several cascaded all-pass networks and it improves sound system quality by eliminating out-of-phase information.
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DIY Microphone Calibration
by Ron Tipton

DIY Microphone Calibration

You can inexpensively calibrate a microphone. How? In this article audioXpress author Ron Tipton discusses two methods of “secondary” calibration: the electrostatic actuator and microphone comparison.
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Build A High-Quality, High-Power Headphone Amplifier
by George Ntanavaras

Build A High-Quality, High-Power Headphone Amplifier

A design based on superior op-amps used in audio applications. A high-quality amplifier must drive high-quality headphones. This article describes the design and construction of a high-quality, high-power headphone amplifier.
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Low-Cost Headphone Amp
by Stefan Dellemann

Low-Cost Headphone Amp

Looking for a headphone amplifier—and a challenge? You can build the design presented in this article with easily obtainable components.
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Test Your Speakers’ Performance with this DIY Measurement System
by George Ntanavaras

Test Your Speakers’ Performance with this DIY Measurement System

In this article, George Ntanavaras describes the design and operation of a system consisting of the ACH-01 accelerometer and a preamplifier with an integrated analog signal processor. With this system, it will be possible to measure at the low frequencies the acceleration, the velocity, and the excursion of a loudspeaker cone. Also the panel vibrations of a loudspeaker cabinet will be very easily obtained. Originally published on audioXpress June 2011.
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Tube Amp Project: The Nardeaux Steromatic 602 S
by John Badalamenti

Tube Amp Project: The Nardeaux Steromatic 602 S

You can build a tube amplifier that's similar to the original Nardeux Stereomatic 302 S. Follow these steps to create a powerful amplifier that produces satisfying music output.
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