All items in category Theory Articles
Measurements Rate New SMT Low-Voltage JFETs Under Consistent Conditions - An Update Using Modern JFETs
by Dimitri Danyuk

Measurements Rate New SMT Low-Voltage JFETs Under Consistent Conditions - An Update Using Modern JFETs

In 2013, Dimitri Danyuk wrote an article that presented apples-to-apples test results for noise densities for several low-noise discrete, SMT, and n-JFETs. In this follow-up article, Danyuk brings us new measurements, updating his design note with measurements of JFET components that appeared more recently on the market. The tests used the same operating conditions so that designers can make a fair comparison for their applications. This article was originally published in audioXpress, December 2018.
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An All-JFET Amplifier: Exploring Modern JFETs Circuits
by Dimitri Danyuk

An All-JFET Amplifier: Exploring Modern JFETs Circuits

This article describes the design and performance of a high-quality DC-coupled all-JFET amplifier. The circuit was inspired by John Curl and Erno Borbely designs and was built with readily available junction-gate field-effect transistor (JFETs) from Linear Systems. The input stage is the the complementary JFET differential pair, the second stage is symmetrical differential amplifier with two pairs of opposite polarity JFETs, and the output stage is a complementary source follower. The amplifier can drive loads up to 150Ω. This article was originally published in audioXpress, October 2017.
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Contextual Awareness: What Is It, and How Is It Being Used?
by Elia Shenberger

Contextual Awareness: What Is It, and How Is It Being Used?

Context-aware devices, such as the embedded smartphone keyboards, have been around for some time, though in a very limited form. By learning regularly used names, locations and phrases, they seem to know your next move, that is, predictive text. Similarly, but at a higher level, the next generation of smart audio devices will combine user-specific data, such as location, preferences and other device sensor data, including audio, to better serve the user.
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Voice Coil Lab Notes: Phase, Group Delay, and Impulse Response - A Quick Primer
by Christopher J. Struck

Voice Coil Lab Notes: Phase, Group Delay, and Impulse Response - A Quick Primer

This short article by Chris Struck (CJS Labs) is mainly focused on the definition and interpretation of phase, helping to make sense of complex data. This reference article is an expanded version of a previous Lab Note published by CJS Labs, and is certainly a great summary of essential knowledge in speaker design. This article was originally published in Voice Coil, December 2020.
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Better Microspeakers Utilizing Hiperco Alloys
by Aminul Md Mehedi

Better Microspeakers Utilizing Hiperco Alloys

This Voice Coil Spotlight article by Aminul Md Mehedi (Senior Application Development Engineer at Carpenter Technology Corp.) explains how the Carpenter-developed high-performance Hiperco 50 and Hiperco 27 soft magnetic alloys can contribute to better performing microspeakers and earphone drivers, improving "decibel (dB) density" in miniaturized consumer electronic devices. This article was originally published in Voice Coil, November 2020.
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The Capacitance Multiplier
by Bill Reeve

The Capacitance Multiplier

In this article for audioXpress, Bill Reeve helps us to make sense of a misunderstood circuit. A capacitance multiplier is useful as a power supply low-pass filter. It is commonly said that, like Miller capacitance, the capacitor’s value in this circuit is “multiplied” by the transistor gain (β) to lower the filter’s pole frequency. The transistor-enhanced filter does that and more, as the article explains in detail. This article, an excellent tutorial on analog circuit design, was originally published in audioXpress, August 2012.
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Searching for a Unicorn Part 2: Generating a Good Signal Source
by Brian Lowe

Searching for a Unicorn Part 2: Generating a Good Signal Source

In this second article, Brian Lowe (Belleson LLC) continues his search for the Unicorn of "Measuring Voltage Regulator Ripple Rejection," this time focusing on the test fixtures. Testing a voltage regulator with exceptionally good performance requires an even more exceptional signal source and measurement setup to measure sub-microVolt ripple across a wide frequency range. Complementing the final article, Jan Didden, offers an informative sidebar about super regulators. This article was originally published in audioXpress, June 2019.
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Searching for a Unicorn Part 1: Measuring Voltage Regulator Ripple Rejection
by Brian Lowe

Searching for a Unicorn Part 1: Measuring Voltage Regulator Ripple Rejection

In this article Brian Lowe shares a fascinating journey in his search for a "Unicorn" that is measuring voltage regulator ripple rejection - or power supply rejection ratio (PSRR). Lowe is the founder and principle engineer at Belleson, LLC, and he has devoted a lot of time to this fascinating "quest." This article was originally published in audioXpress, May 2019.
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Practical Test & Measurement: Mastering Wireless Multi-Tone Testing
by Andrew Taylor

Practical Test & Measurement: Mastering Wireless Multi-Tone Testing

This article explains the issues resulting from measuring a wireless audio connection and how wireless multi-tone testing can help us to overcome those obstacles. The article is particularly focused on the needs of manufacturers and designers of modern wireless audio devices and offers valuable insights on multi-tone testing, a technique that has been around for many years, and which Klippel perfected in its own multi-tone measurement module (MTON). This article was originally published in audioXpress, December 2020.
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Practical Test & Measurement: What to Measure for Quality Control of Audio Devices
by Dan Knighten

Practical Test & Measurement: What to Measure for Quality Control of Audio Devices

In this Test & Measurement article from Dan Knighten (Audio Precision), the author focuses on the practical question of manufacturing test strategies and objectives and shares what measurements reveal about the device under test, offers suggestions for specific measurements, and provides techniques for various devices and scenarios. This article was originally published in audioXpress, November 2020.
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