audioXpress Magazine      May 2021

  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.

Comment
4 From The Editor's Desk 
A New Window For Vacuum Tubes
Editorial By J. Martins, Editor-in-Chief

Glass Audio
8 The Original Western Electric 300B Vacuum Tube
Now Shipping Worldwide
By Richard Honeycutt
audioXpress provides an inside look at Western
Electric, which has reestablished operations due to
the resolve of entrepreneur Charles Whitener. The
company now based in Rossville, GA, recently created
a new and re-imagined electron tube works facility
with the goal to resume manufacturing the 300B
single-ended triode tubes, and reintroduce its flagship
product to market.

14 Using Chaffee's Method Of Load Lines
By Scott Dorsey
In this article, Scott Dorsey recalls a rapid and ingenious
way to use load lines to easily predict tube circuit operations.

20 Experimenting With Tube Sound
By Bill Reeve
Learn how automatic gain control applied to solid-state
and vacuum tube audio paths enable interesting
design, construction, and listening experiences in this
easy-to-build stereo preamp.

26 The Cranberry
A Versatile Stereo Vacuum Tube Amplifier
By Bruce Heran
In an effort to expand his DIY amplifier collection,
Bruce Heran designed this stereo vacuum tube
amplifier using a concept that originated in the 1940s
and was initially intended for a budget amplifier.

Columns
Audio Scope
36 Determining The Real Output Current For
Op-Amps And Fully Differential Amplifiers
By Michael Steffes

Hollow-State Electronics
60 Vibrato and Tremolo
By Richard Honeycutt

Features
40 Measuring Vibration With Piezoelectric Sensors (Part 2)
Design And Construction
By George Ntanavaras
In this article series, George Ntanavaras describes his research on
measuring vibration using Piezoelectric Sensors. In the second part,
he discusses the design of such a system, configurations of the
charge amplifiers circuits that he built and tested, and the
connections to the piezoelectric sensors. He also presents some
additional sensors that could be used for vibration measurements.

48 Noise Is Everywhere — Even In MC Input Transformers (Part 1)
A Special Survey For The Skeptics
By Burkhard Vogel
In this article, Burkhard Vogel discusses the signal-to-noise (SN)
measurements of moving coil (MC) phono amps. He thinks it is good
practice to measure a transformer with an input load and he wants
to prove that an MC step-up transformer (SUT) produces noise
because of its insignificant impedance.

54 The Science And Physics Of High-End
Mic-Preamp Design (Part 4)
Different Approaches
By Mike Meechan
In previous articles, Mike Meechan considered the fundamental physics
that play a rudimentary part in microphone preamplifier design, and
explored its inhabitancy in the real world to retain the fidelity of the
mic signal along its path from transducer to output. At this stage,
he continues to look at what (theoretically) contributes to perfect
active mic preamps.

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