Barney Oliver: Crossover Distortion in Class B Audio Amplifiers
This is the famous analysis of class B amplifier cross-over distortion by the then head of HP Reasearch Labs, Dr. Barney Oliver, published in the February 1971 edition of the HP Journal. The bias current Iq for a class B emitter follower amplifier is shown to be approximately Iq = .026/(Re+re+(rb/hFE)). In practice, – the […]
Baxandall’s Original Tone Control Article from Wireless World 1952
This article was published in October of 1952, when Baxandall was 31 years old, the design having already won him a prize 2 years earlier in a competition. His design basically relegated other tone control circuits to the scrap heap, although cheap passive, or non-inverting circuits still persisted well into the 1980’s, especially in low […]
OPEX-1: A Discrete OPAMP for Audio
This design showcases a discrete opamp for audio applications. It features very low noise, low distortion and a class A output stage that will deliver 1ppm distortion into a 600 Ohm load at 12 V peak. OPEX-1-Discrete-Opamp
The Alexander Amplifier
Mark Alexander’s eponymous creation was an early example of a high performance CFA amplifier and used an ADI integrated opamp and IGBT output devices in a novel circuit configuration that, at the time, yielded vanishingly low distortion and blistering speed. The ‘Alexander’ amplifier has been recycled by practitioners numerous times since its initial publication with […]
X-Altra Mini One Line Preamplifier
The X-Altra Mini One is a simple line preamplifer based on the National Semiconductor LM4562 (also known as the LME49720) that I built around 2008 and which served me well until about 2014 when it was replaced with newer more sophisticated designs. Nevertheless, this simple preamp sounded very good, and thanks to the LM4562 (which […]
Stochino Feed Forward Amplifier – Wireless World 1994
This article decribes a feed forward amplifier concept from Giovanni Stochino. The design, while novel, is very complicated and delivers about 30 dB in distortion reduction. Stochino Feed Forward.pdf For an altogether simpler alternative that acheives about 20 dB distortion reduction, take a look at AFEC (‘augmented feedback error correction’) elswhere on this site.