Using the QuantAsylum QA401 for accurate Audio Measurements

The QA 401 from QuantAsylum (superseded by a newer, improved QA 402 and now the QA403) has emerged as a popular, comprehensive audio test instrument in the DIY audio fraternity and the go to instrument in many cases for commercial production testing in the audio industry. It combines a first rate DAC and ADC with […]

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Building Quiet Audio Power Amplifiers Requires Best Wiring and Layout Practices

There is a misconception that noise pickup is reduced by placing the input RCA connectors (and similarly XLR input connectors in a fully balanced system) on opposite sides of the amplifier rear panel and then running short wires to the amplifier modules. This arrangement is the worst of all worlds. The internal loop areas available […]

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Fast transimpedance aka Voltage Amplifier Stages for Audio Power Amplifiers

Here is a quick look at some of the problems that can occur when the VAS (aka TIS) in an audio amplifier is driven into saturation without considering the effects of base charge storage – a phenomena all bipolar transistor suffer from.

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RIAA Equalizer Amplifier Design

This article explores the fundamental’s of phono amplifier design,  culminating in a few practical designs. Special emphasis is placed on overload margins (critical if you want good sonics from your EQ amp), driving the EQ network adequately and noise. RIAA Equalization Amplifiers V2.0 Below is the RIAA Calculator Excel spread sheet.  Please read the article above, […]

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Ground Loops

Updated with new material 7th January 2019 This set of c. 70 slides is the culmination of my experience over a period of about 25 years building numerous power amplifiers and preamplifiers. I first started out in audio around 1975 or 76 a teenager. Some of my creations were reasonably quiet – through pure luck […]

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MC Head Amp Circuit Compendium

Here is the new updated moving coil head amp designs compendium – updated 31 July 2019. The first file is a PDF compendium of about 28 different circuits with noise, distortion and current consumption details. All the LTspice sim files are zipped in the second file. What is immediately apparent from this is that having […]

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