CFA Diamond Buffer IPS: Does it Operate in Class B or class A?

There is a persistent assertion by small group of amplifier design practitioners that the diamond buffer input stage of CFA audio amplifier operates in class B (or AB) mode wherein there is a hard ‘handover’ between each half of the diamond buffer input stage as the input signal passes through 0V.  The most recent claim […]

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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 […]

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Stan Curtis 60W Class A Amplifier from ETI

Stan Curtis was involved in both engineering and management roles in companies like Quad, Cambridge, Rotel (a family owned Japanese brand) Mission and Lecson to name a few. He is primarily an audio business consultant and remains highly respected and a noted product designer within the sector in his own right. This is his 60 […]

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Solid State Relay with PCB Layout

A complete relay that is smaller than a Tyco RT series EMR Simple_solid_state_relay_Updated  . This design uses a small double sided PCB and some SMD components. Here are the Gerber files SSLR.  The recomended mosfets for this design are the  PSMN4R3-100PS[1] for supply rails of up to +-50 V absolute maximum, and for supply rails of up […]

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Augmented Feedback Error Correction (AFEC)

AFEC is a simple technique that augments the feedback of an amplifier to dramatically improve the Large Signal Non-linearity (LSN) distortion performance by up to 20 dB across the audio band. Additionally, AFEC acts to remove any DC offsets and also improve PSRR significantly. Augmenting the feedback in a manner similar to that described in […]

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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 […]

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