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Author: bonsai
Richard Lee’s Ultra-Low Noise MC Head Amp
This design was a development of Marshall Leach’s MC head-amp from the 1970’s and to my knowledge, Richard Lee’s implementation presented here has not been bested in terms of noise – about 280pV/rt Hz in a well implemented exemplar other than in the Hifisonix X-Altra MC/MM Phono Preamplifier. Importantly, it requires only about 12mA current…
My Loudspeakers
I bought a pair of B&W 703’s in about 2003 and they travelled with me all around Asia when I worked there as an expat for ten years. These are big loudspeakers with fantastic bass and mid-range articulation. The treble may be a little forward for some, but for Jazz, big band and rock they…
The Endless Semantic Debate: Current and Voltage Feedback Amplifiers
It seems some are still agonizing over the ‘current feedback’ versus ‘voltage feedback’ definition. Clearly a case of people wanting to continue to flog a horse that was laid to rest five decades ago during the heyday of the analog computer, or they simply fail to grasp the CFA concept. I suspect there are an…
The Tale of Two Recordings
I thought I’d share my thoughts with you on the sound of two LP’s I recently acquired. Many of you will have heard of the term ‘sound wars’ which has been coined to describe the relentless increase in the use of dynamic range compression in modern recordings, a development it could be argued from the…
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:- …