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Category: Articles
JLH 10 Watt Class A Amplifier
This is a copy of the original John Linsley-Hood article that appeared in Wireless World in 1969. This design, almost 50 years old, is still built in its hundreds all over the world. A quick root around on the web will show numerous kits, many of quite acceptable quality, emanating from China and Hong Kong.…
Class A Buffering the Correct Way
Here’s a simple way to force an opamp output stage to run in class A when used with a discrete buffer output stage – it takes just 1 resistor to provide a near constant current source load. Operating the opamp (and the output buffer stage) in class A dramatically reduces harmonics on the power rail…
Hifisonix ‘Symphony’ Line Preamplifier
I designed and built this preamplifier while living in Taiwan a few years ago. The Symphony preamp features Baxandall tone controls, up to 7 inputs, a class A 2 W headphone amplifier and a Goldpoint 24 position attenuator. The write-up describes the design process and choices in some detail and my listening impressions: Part 1…
Ovation e-Amp: A 180 Watt Class AB VFA Featuring Ultra Low Distortion
The e-Amp is a 180 Watt RMS (very conservatively rated into 8 Ω ) fully balanced symmetrical (‘FBS’) amplifier featuring an emitter follower triple (EFT) bipolar output stage and beta enhanced VAS stage. The amplifier can be configured using jumpers for TMC (Transitional Miller Compensation) or straight Miller compensation (MC). The VAS can be lightly…
Disc Recording Equalization Demystified by Gary A. Gallo
Pictured: A Neumann Cutting Lathe used to make the record master. Picture courtesy of Bakery Mastering This is one of the best non-mathematical introductions to the RIAA disc recording playback chain written. Gallo worked at the Crane School of Music in New York for 30 years as an audio engineer, where he also received a…
Ovation 250 Power Amplifier
The Ovation 250: A 250W per Channel Audio Power Amplifier (updated 1st June 2013). This amplifier was designed and built in 2005/2006 as my first foray back into audio design after a nearly 20-year hiatus, This write-up was originally published in 2009 when I was living in Tokyo, Japan. Introduction Diy Audio is a wonderful activity:- …
CFA vs. VFA: A Short Primer For the Uninitiated
This article was written in 2014 in response to what can only be described as a vitriolic debate as to what constituted a CFA on diyAudio.com. At the time, many of the participants were struggling to grasp the fundamental differences between VFA’s and CFA’s, and even how to tell them apart. So, this document is…
Audio Power Amplifier Design – Peter J Baxandall
In this 6 part series of articles published from January 1978 in the now defunct Wireless World magazine, Peter Baxandall takes the reader through some of the fundamentals of audio amplifier design as they were understood at the time. Baxandall_Audio Power Amplifier Design In 1978 there was still much discussion about feedback and how to…
Douglas Self’s 8 Distortions and a Few More
(pictured above is the hifisonix 180 Watt per channel e-Amp) No one had codified all the major audio amplifier distortion mechanisms until Douglas Self published the first edition of his ‘Audio Power Amplifier Design Handbook’ or APAD’ as it has become known, in 1996. He used a standard Lin* topology amplifier and then proceeded to…
The Theory of TIM – Matti Otala
Matti Otala follows up on earlier research on the subject of TIM. The Theory of TIM Matti Otala