Preamp Muting Circuit

Oftentimes a muting circuit for the output of a preamp is left out of DIY applications as an unnecessary or annoying part of the project. This is usually due to the lack of awareness that a simple circuit can perform such a duty. Anyone who occasionally forgets to turn the power amp on last, or switch it off first, endures the annoying thumps and noises that often occur from the preamp upon power cycling. This article proposes a simple circuit for preamp muting. The article was originally published in audioXpress, March 2010.

With many audio manufacturers and consumer electronic companies experimenting development with voice recognition applications, Google naturally wants to make it easy as possible for anyone to get familiarized with the company's Google Assistant SDK, to implement voice interaction. Billy Rutledge, Director of AIY Projects at Google, recently revealed a new voice recognition DIY kit and voice HAT for the Raspberry Pi.

This project is based on a previous audioXpress article: “A Solid-State Single-Ended Power Amp” by Ed Simon, published in the April 2006 issue. Ron Tipton was deeply impressed with this amplifier project which used only five transistors per channel, two of them being current sources. This article was originally published in the old audioXpress website as a PDF, but was never reposted. Now we make available online with updated references and links.

In this simple amplifier project, Ed Simon describes a Class-A amplifier design that mainly intends to reproduce music with reinforced emotional expression. That's what you normally get with a quality design, but to achieve it, the author shares the complete concept, power requirements, circuit topology, construction and testing of this single-ended amp... in a solid-state design. This article was originally published in audioXpress, April 2006.

At the 139th AES convention in New York, Solid State Logic announced the introduction of βeta, a unique 500 format module Hardware Development Kit using SSL specific components. Now audio electronics enthusiasts can build creations that will look as cool as they sound and feature real SSL controls.

Here is a simple portable device from George Ntanavaras that can help answer the question about peak voltage and peak current requirements and whether or not your power amplifier is capable of driving your loudspeaker without clipping. This article was originally published in audioXpress March 2015 — Focus on Test & Measurement Edition. (Updated Dec 2015)

Here’s a do-it-yourselfer’s dream in tube amp design: four operating modes, high quality, low cost, and low distortion. An article originally published by audioXpress in May 2007. A true versatile project which we think deserves to be shared.

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.

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.”

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