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

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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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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 […]

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Ovation SCA-1: A high performance fully balanced line pre-amplifier

  Originally published in 2010 Here is the result of my investigation in to a fully balanced high performance, low distortion line pre-amp, the ‘Ovation’ Stereo Control Amplifier One’. I drew some inspiration for this project after reading about the TEAC Esoteric line preamp, which is also based on the TI PGA2320, and received rave reviews […]

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Small Signal Audio Line Stage Buffer/Headphone Amplifier

This design, which I completed in 2010, takes an LM4562 and marries it to a hefty single ended class A output stage, which can be biased up for either 50 mA or 110 mA. The output stage is included in the global feedback network and can achieve 1 ppm at 20 kHz  into 600 Ohms […]

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