audioXpress Magazine      May 2022

  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.

From The Editor's Desk
4 From The Editor's Desk
The End Of Cheap Tubes
The Ukraine / Russia news is having a significant
impact on the global supply of vacuum tubes.
Editorial By J. Martins

5 Client Index

Features
16 Orchard Audio Starkrimson Stereo Ultra
Pushing Power Amplifier Performance Boundaries
By Stuart Yaniger
Leo Ayzenshtat, the founder of Orchard Audio, took
GaN Systems' gallium nitride (GaN) power transistor
technology, which Stuart Yaniger evaluated for
audioXpress in the April 2022 issue, and designed his
Starkrimson Stereo Ultra audio amplifiers. Of course,
Stuart Yaniger had to investigate.

48 An Introduction to Testing Vacuum Tubes (Part 2)
Choosing the Right Tube Tester
By Mark Driedger
Part 1 of this article covered how tubes fail and wear
out, and their key characteristics. In this continuation,
the article discusses how tubes are tested, the
different types of tube testers, and selecting a new
commercially available tube tester.

54 Building a Guitar-Controlled Synthesizer
Frequency to Volts and Back
By Ethan Winer
This is the second article in a DIY journey of a
guitar-controlled, all-analog synthesizer project that
will include multiple stages and modules. Following a
Sample & Hold circuit designed to retrieve previous
voltages that no longer exist, this article details
voltage control and how the playing is converted to
voltages and back to frequency.

Columns
Sound Control
44 Effect of Air Conditions On Sound Propagation
By Richard Honeycutt
Sound systems need to be readjusted under variable
atmospheric conditions, affecting temperature,
relative humidity, and barometric pressure. This
article discusses how these changes affect different
acoustical parameters and what can be done to adjust
for the changes.

Hollow-State Electronics
62 Graphical Analysis Of Class-A Amplifiers
Developing a Love of Designing
Hollow-State Electronics
By Richard Honeycutt
This article discusses optimizing an audio amplifier
for B+ supply voltage; voltage gain; and distortion
behavior, eventually aiming for a Class-A stage to
achieve the best performance.

Market Update — Phono 2022 Report
8 The Enduring Appeal of Vinyl
By J. Martins
Sales of vinyl records are again a respectable revenue
source for the music industry, representing more than
$3.4 billion of the $26 billion USD in global revenues
achieved in 2021. This market update discusses record
players and related products available for all price segments.

Glass Audio
22 Birds Of A Feather
Western Electric's New Production 300B
By Michael Boele
This is the highly anticipated long-term review of a pair
of 2021 new production 300B directly heated power triodes
made in Western Electric's production facility at Rossville,
GA. Michael Boele received a pair to test at the end of
March 2021, and has been extensively using them since they arrived.

38 Meet The Pentriode
By Alan Kimmel
This article delves into the concept of connecting commonly
available pentode tubes as triodes, creating a circuit that
excels in linearity. The author proposes different possible
approaches, including for a mu stage.

40 Adding Bluetooth To A Tube Amp
By Merlin Blencowe
Some may find it heresy, but these days we can buy tube amps
with Bluetooth, Wi-Fi, or LAN connectivity installed. In this article,
Merlin Blencowe details how to derive +5V from an existing
heater circuit without upsetting things and allowing us to connect
existing modules with Bluetooth, Wi-Fi, and more.

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