hifisonix

Tag: amplifier

  • Hifisonix HPA-1 Class A Headphone Amplifier

    The circuit combines a dual ultra-low distortion opamp, the LM4562 or OPA1642, with a class A discrete power output stage to deliver outstanding performance both measured, and sonically. The complete amplifier, including the opamps, runs in class A. Into 60 Ohm headphones and above, the HPA-1 remains fully in class A up to the rated…

    Read more

  • The Theory of TIM – Matti Otala

    Matti Otala  follows up on earlier research on the subject of TIM. The Theory of TIM Matti Otala

    Read more

  • Review of Bob Cordell’s Book ‘Designing Audio Power Amplifiers’

    ‘Designing Audio Power Amplifiers’ by Bob Cordell  – Reviewed by Andrew C. Russell in 2011 Bob Cordell (on the right) pictured with Jan Didden, publisher of ‘Linear Audio’ After a 15 year hiatus from electronics, I returned in 2005 to linear design not as a professional but as a hobbyist. Earlier in my career, I…

    Read more

  • 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…

    Read more

  • Output Coupling Inductors

    Inductors on the output of an amplifer are used to isolate the amplifer from capacitive loads at HF and ensure stability.  There has been quite some debate on DIYaudio.com as to whether they are audible, necessary, or just the result of designers being overly cautious.  Some very well known designers in the field have decided against using…

    Read more

  • The Monolithic Op-Amp: A Tutorial Study

    This was an invited paper at the ISSCC in 1974 by James Solomon, who at the time worked for National Semiconductor (acquired in 2011 by TI). Those were heady days in semiconductors, with major process and circuit design breakthroughs taking place at breakneck speed. The general purpose microprocessors’  pivotal role in powering the Apple II…

    Read more

  • Feedback Analysis by Marshal Leach

    Here is a short write up by Marshal Leach (RIP) on feedback analysis.   fdbkamps

    Read more

  • 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.

    Read more