It has been intriguing to watch the renewed interest in the 300B triode for audio circuits. A descendant of the 300A originally produced by Western Electric, it has in recent years taken on an almost mystical reputation with certain audiophiles. There are many interesting stories of the 300B on the Internet.
One of my friends, David Berning, has been building very high-quality vacuum tube audio amplifiers for many years. He has used many different tube types, but the fundamentally outstanding feature of his designs is his patented ZOTL technology. One of the factors that is imperative in getting good performance from a vacuum tube amplifier is the process of converting the high impedance of the tube to the low impedance of the speaker in a manner that preserves the frequency response, phase, and low distortion of the active device. The most common method of getting this impedance match is the use of a transformer. We will take a closer look at transformers and the factors such as leakage inductance, interwinding capacitance, hysteresis, saturation, and others that make it very difficult and costly to build a wide bandwidth transformer free of gremlins.
Transformer Basics
Over the years, audioXpress has had several excellent articles describing transformers and their applications in audio. The most recent article series is listed in Resources and it references a number of additional articles. They contain a wealth of knowledge on transformer design, materials, construction, and compromises.
Two of the most important aspects of transformers in audio use are for electrical isolation and impedance conversion. Let's look at isolation first.
Isolation
This story is from the May 2023 edition of audioXpress.
Start your 7-day Magzter GOLD free trial to access thousands of curated premium stories, and 9,000+ magazines and newspapers.
Already a subscriber ? Sign In
This story is from the May 2023 edition of audioXpress.
Start your 7-day Magzter GOLD free trial to access thousands of curated premium stories, and 9,000+ magazines and newspapers.
Already a subscriber? Sign In
Perspectives on Automotive Sound Design - In the Era of Electric Vehicles
From combustion engine vehicles to fully electric vehicles, and from sound systems in the car to sound design and synthesis for the car itself, everything is changing in the automotive industry. This conversation with two members of the DSP Concepts automotive team with vast experience in the field, John Whitecar, VP of Product Management, and Steve Ernst, Head of Business Development, offers valuable insights on how things are evolving.
Audioscenic: From Vision to Product
Audioscenic is an innovative 3D audio beamforming technology company spun off from the University of Southampton. It is a remarkable example of perseverance, from early development to the first commercial implementation, which audioXpress considered Best of Show at CES 2023. This article shares the story so far, as Audioscenic continues its groundbreaking journey exploring consumer applications for its forward-thinking approach to spatial audio.
The Changing Audio-Ecosystem in Electric Vehicles
The rapid shift to plug-in hybrid and full-battery electric vehicles is having a significant and long-lasting impact on how audio systems are integrated into cars. While some noises are much more prominent due to the absence of the familiar engine noise, the transition offers exciting possibilities for sound systems, passenger entertainment, and enhancing the overall automotive experience.
A (Z)OTL with 300Bs: Part 1-The Makeover
Rebuilding an amplifier for reasons of better reliability, better aesthetics, or bringing it up to the latest standard can be very rewarding. And if it is a classical, technological grandstand, even more so. Thomas Perazella embarked on such an adventure with a famous David Berning ZOTL amplifier. In Part 1 of this article, Tom presents the amplifier and discusses its unique circuitry. In Part 2, he will proceed to dismantle and rebuild the amp for the new owner and place it in a new chassis
The Hypex NCORE NCx500 Amplifier Module
NCORE (NC) amplifier modules are the flagship product from Dutch manufacturer Hypex Electronics and its success among the high-end audio brands is well documented. In 2022, Hypex announced the introduction of its improved NCOREX technology, starting with the NCx500 OEM module, which audioXpress received for review
Monoblock Power Amplifier with Precision Bias Control
In Part 2, Bruce Gillingham discusses the remainder of the MB1's circuitry, its mechanical design, and its performance measurements
A Trip Down Memory Lane
The history of tube application began with radio receivers, the telephone system, and cinema sound systems. Later, tubes began to be used in home stereo systems, and in amplifiers for electric guitars. Today, the primary markets for tubes are high-end stereo and musical instrument amplifiers. In this article Richard Honeycutt remembers his first contact with \"starter\" guitar amps as a teenager, progressing throughout his days as a semi-pro musician
The Vanderveen Trans PP80 Valve Amplifier
This new push-pull (PP) valve amplifier, featuring the Trans technique, delivers 80W power, refined resolution, valve-sound envelopment, and low distortion plus good speaker damping. And... the amp is simple to construct
Accuracy in LTspice Modeling
Sometimes we need to consider the human factor when using circuit design simulation tools. In this article, our hollow-state expert details an error that occurred in a past article, which is now being corrected.
Transitioning Audio Tests from R&D to the Production Line
Production line audio testing poses many challenges such as noisy environments, harsh operating conditions, high throughput, relative limits, and more. In this article, Steve Temme shares his observations and outlines the main considerations to ensure a successful operation.
