audioXpress Magazine May 2026

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audioXpress Magazine May 2026

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.

Hear No Evil
A better perspective concerning the future of vacuum tubes.
Editorial By J. Martins
I was asked recently about the AXPONA and High End Vienna shows by someone who sees the audio industry purely from a business and investment perspective and never attended a "high-fidelity" show in his life. I described the profile of companies exhibiting, the number of manufacturers and brands, and the range of prices involved currently in "high-end audio" products. When I mentioned that the majority were manufacturers from the U.S., Canada, or Europe, he reacted with the greatest of surprise and his immediate question was "and are they doing alright?". This is a common reaction I get even from technology professionals that are not at all familiar with the world of home audio, even though many admit to being aware of some luxury audio brands when I mention them. In this specific conversation, when I described the business environment in that market segment—generously including a broader spectrum of brand examples with varying prices—the next question I got was something on the lines of "...and will they still be around much longer?" I understand it. The idea that there are companies in Oregon, Texas, France, Germany, Poland, or Switzerland building handcrafted wood cabinets and circuit boards, employing between 10 and 100 people....
---> Hear No Evil.

5 Supporting Companies

Glass Audio
8 Designing the Dynaco ST-70 Series 3 Vacuum Tube Audio Power Amplifier
By Dan Fraser
Having created a new version of the Dynaco ST-70
Power Amplifier that received excellent reviews, Dan
Fraser details what makes an audiophile-grade tube
amp special, using the Series 3 as an example.

14 The Yin & Yang Circuit
By Geert Oyen
Geert Oyen ran into a circuit that seemed an obvious
building block on one side, but a well-kept secret on
the other side. In this article, he analyzes the basic
circuit and shows two implementations of the circuit.

22 Stabilizing Tube Feedback Amplifiers Without Much Math
Part 1—Diagnostic Principles
By Merlin Blencowe
This article introduces feedback stability theory for
tube amplifiers using practical gain/phase plots.
Part 1 establishes diagnostic principles.

30 Rediscovering The EF184
A Surprising MM RIAA Preamplifier
By Zoran Dukic
This project resurrects the EF184 as a triode for a
moving magnet (MM) RIAA phono preamp design.
Connected as a triode, the EF184 operates linearly,
matching high-quality audio triodes. The design,
leveraging leftover parts, demonstrates how
overlooked vintage tubes can deliver exceptional
performance in modern audio circuits.

36 Building a KT170 Class-A Amplifier
By James Skov
This article documents a Class-A KT88 / KT170 single-ended
tube amplifier design inspired by a vintage
1955 Fender Champ rebuild.

44 Thoughts On Igor Popovich's
Audiophile Vacuum Tube Amplifiers Books
By Mark Driedger
Mark Driedger reviews Igor Popovich's three-volume
Audiophile Vacuum Tube Amplifiers series, which he
confirms to be "the most comprehensive modern DIY
book on vacuum tubes."

48 Revisiting An Elegant Idea
The Augmented Follower
By Dimitri Danyuk
Dimitri Danyuk revives James Ross Macdonald's 1957
augmented follower patent in solid-state form. With
two implementations tested and measured, it's a
compelling demonstration of elegant topology over
corrective feedback.

Features Departments
54 New Expressions For First-Order Filter Phase Response And Group Delay
Part 2—Deriving Responses And Group Delays
By Barak Shpiez
Textbook digital signal processing techniques are shelved
in favor of simpler analysis that relies on trigonometry
and algebra. This process reveals how filters affect signals
in a more tangible way while revealing new forms of the
phase response and group delay formulas. In this second
part of the article, we'll combine the first-order feedforward
and feedback filters to derive the gain response, phase
response, and group delay for the shelving filter. We'll then
see how these expressions can also be used for comb and
all-pass filters too.

Columns
Hollow-State Electronics
63 Hermon Hosmer Scott
A Visionary, Engineer, and Entrepreneur
By Richard Honeycutt
On this trip down memory lane, Richard Honeycutt discusses
the life work of Hermon Hosmer Scott whose company's
engineering-first approach and more than 100 patents defined
hi-fi as a consumer category.