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Category: Articles
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…
Hifisonix Solid State Loudspeaker Relay
On big power amplifiers, conventional electromechanical relays leave much to be desired when it comes to their ability to reliably switch fault level currents in the event of a catastrophic amplifier fault. In a worst case situation (and I speak from experience), one of the output devices fails short circuit, placing the full amplifier rail voltage across the loudspeaker terminals. Relay…
Opamp Noise Visualizer
This Excel spread sheet tool was developed from one by Steve Hagman (www.AnalogHome.com) and allows en and ien data for up to 7 opamps to be compared. When using the tool, make sure you enter comparable data – so for example, always use the same frequency to make the comparison. I normally use 1 kHz…
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…
Tom D Kite Busts Some Audio Myths!
Ever wondered how we got to ‘feedback is bad’, ‘ . . . sampling destroys the music’ or ‘ . . . analog is 40 bits resolution . . .’ , ‘we need damping factors of 1000’ and ‘ . . . only vinyl sounds good’ ? Tom D Kite PhD, of Audio Precision, takes…
AN-597 Current Feedback Amplifiers
This National Semiconductor application note was written by Hans Palouda and published in 1989. It explains basic CFA operation clearly and concisely. AN-597 Current Feedback Amplifiers Here are some other useful application notes and articles that may help in developing an understanding of amplifier topologies and their associated trade-offs. wiki https://en.wikipedia.org/wiki/Current-feedback_operational_amplifier EDN https://www.edn.com/design/analog/4458753/In-defense-of-the-current-feedback-amplifier ADI https://www.analog.com/media/en/training-seminars/tutorials/MT-034.pdf TI https://cas.ee.ic.ac.uk/people/dario/files/E416/OA-30.pdf …
CFA’s: An Intuitive Analysis from Intersil
This application note from Intersil provides a simple and easy to understand explanation about CFA operation CFA – An Intuitive Analysis
Feedback Analysis by Marshal Leach
Here is a short write up by Marshal Leach (RIP) on feedback analysis. fdbkamps
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…
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.