audioXpress Magazine      May 2023

  audioXpress remains the authority on audio and reproduced sound by connecting manufacturers and distributors with developers, buyers and consultants around the globe! It's readers are the audio product designers, consultants, integrators, DIY enthusiasts, opinion leaders and your best customers. All of them agree that the coverage of trending topics, unique in the audio industry, make audioXpress a must read.

Every month, audioXpress combines the best educational articles on topic such audio electronics, speaker and headphone design, amplifiers (from tube to Class D), acoustics, practical test and measurement, audio engineering praxis, and standards. audioXpress provides inside stories on new audio developments, on R&D Stories, the most complete objective reviews of innovative products and software, and selects some of the best DIY audio projects from worldwide experts.

4 Make It Worth It!
Thankfully, products announced about a year ago are finally becoming available.
Editorial By J. Martins
In this Glass Audio special issue of audioXpress we are proud to offer two high-quality tube amplifier projects from two renowned tube experts from both sides of the Atlantic. The first project by Menno van der Veen is another amplifier designed under the auspices of the author's TubeSociety initiative. The other comes from Thomas Perazella and in this case details a remake of a famous David Berning ZOTL amplifier. Both are of remarkable quality and value to all tube/valve enthusiasts at a time when it becomes increasingly more risky (and expensive) to build your own projects, unless we already know that the results are truly exceptional.
---> Make It Worth It!

5 Supporting Companies

Features
8 The Hypex NCORE NCx500 Amplifier Module
Doubling Down on a Flagship
By Stuart Yaniger
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.

18 Learning Audio Testing And Measurements
Review by Jan Didden
Our technical editor Jan Didden explores Igor
Popovitch's book, Audio Tests & Measurements, and
provides his thoughts on its value to our readers.

44 Vintage Op-Amp Noise Simulation
Part 2 — Calculations and Noise Sources
By Burkhard Vogel
In Part 1 of this article, Burkhard Vogel presented the
deviations from realistic noise figures in datasheets,
based on measurements and calculations for real OpAmps.
In this second part, the findings are expanded
through the use of Mathcad calculations, culminating
in an accurate Spice model for the noise sources, and
a conclusion about noise source correlations.

50 Monoblock Power Amplifier With Precision Bias Control
Part 2 — Circuitry, Mechanical Design, and
Measurements
By Bruce E. Gillingham
This project describes how to build a high-power
(300 Watt into 4 Ohm), bipolar, Class-AB, monoblock audio
power amplifier. In Part 2, Bruce Gillingham discusses
the remainder of the MB1's circuitry, its mechanical
design, and its performance measurements.

59 Power Transformer Parameters, Selection, And Testing
Part 7 — A Few Transformer Core Types and
Their Advantages and Disadvantages
By Chuck Hansen
This article series continues to explore the history
of transformer cores, construction methods and
materials, and the various technical parameters of
transformers. Part 7 looks at the various transformer
core types, their advantages and disadvantages, and
the coil winding machines used to make them into
transformers.

Glass Audio
20 The Vanderveen Trans PP80 Valve Amplifier
By Menno van der Veen
This new push-pull (PP) valve amplifier, featuring the
Trans technique, delivers 80 Watt power, refined
resolution, valve-sound envelopment, and low
distortion plus good speaker damping.
And... the amp is simple to construct.

30 A (Z)OTL With 300Bs
Part 1 — The Makeover
By Thomas Perazella
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, he presents the amplifier and discusses
its unique circuitry.

38 Myths In Tube Circuit Designs
By Peter Dieleman
In the world of tube amplifiers a number of myths
and misunderstandings repeatedly show up.
In this article, Peter Dieleman will demystify
and debunk them.

Columns
Hollow-State Electronics
63 A Trip Down Memory Lane
Electric Guitar Amps
By Richard Honeycutt
The history of tube application began with radio receivers,
before being used in stereo systems and electric
guitar amps. In this article Richard Honeycutt remembers
his first contact with "starter" guitar amps, progressing
throughout his days as a semi-pro musician.

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