The origins of the Glass Audio Special that audioXpressfeatures in May every year, goes back to our magazine’s roots when Edward T. Dell, Jr., founded a quarterly periodical called Glass Audio, in 1988. That magazine reflected an increasing interest for tube-based audio electronics and in this edition, we revisit the reasons why the interest in tube electronics was so strong at that time - and why dissatisfaction with the sterile sound of the Compact Disc and the early digital recordings had much to do with it… This May edition of audioXpresscontinues to be a favorite among tube and audio electronics aficionados, carrying on the “Glass Audio” tradition up to the present day.
For this Glass Audio Special issue, Menno van der Veen, continues to detail the TubeSociety-2A3-300B-SE amplifiers. van der Veen designed five challenging 300B-SE amplifiers for his students, who are learning to become the best designers and constructors of tube amplifiers. In Part 1 of his article, van der Veen explained how his TubeSociety academy in the Netherlands designed the first four amplifiers. The fifth amplifier, plus information about the power supplies and construction, is the focus this month, and we are certain our tube-oriented readers will appreciate it.
Also as part of our Glass Audio focus, Patrick Brunner discusses DIY Tube Amp Heat Management and illustrates some methods to greatly increase the performance and reliability of a DIY tube amplifier. And another of our tube experts, Gerhard Haas, shares what he knows about output transformers, probably the most important component of a tube amplifier. In the first part of his in-depth article, he explains the fundamental properties of transformers and examines the most important criteria for rating and building a transformer.
We also interview Jason Stoddard, the heart and mind of Schiit Audio, a unique company that has managed to achieve a solid reputation for its high-quality products available at reasonable prices. And Stoddard knows a thing or two about tubes...
Of course, Richard Honeycutt’s column on Hollow-State Electronics complements this special edition quite well, with his article "Comparing Output Waves of Tubes, FETs, and BJTs." In his March 2018 Hollow-State article, Honeycutt examined the characteristic curves for vacuum triodes and pentodes and field-effect transistors (FETs) and bipolar junction transistors (BJTs), with a view toward understanding why they have different distortion signatures. In this new article, he compares the behavior of those circuits.
And because it can’t be just about tubes, in this same edition Andy Lewis (Acme Sound, LLC) starts an original look at Back EMF Phase Relationships in Moving Coil Loudspeakers - Identifying, Quantifying, and Modeling Back EMF. In this three-part article, the author explores the generation of Back EMF in the region of a loudspeaker’s resonance. He also demonstrates a method for calculating the position of the moving assembly (or “cone”) relative to input signal, using complex impedance measurements.
Finally, Ron Tipton starts examining Master Quality Authenticated (MQA) recordings, measuring what exactly is in that high-frequency content, which is folded, “origami fashion,” into the low-frequency region. An MQA decoder (DAC) unfolds the highs back to their proper spectral location. The theory sounds great but because we can’t directly hear this upper register, how do we know what’s actually there? Ron found a way and shows what he found.
audioXpress May 2018 also reviews the latest book by Richard Honeycutt (yes, him), “Acoustics in Performance,” where our esteemed colleague details “all you need to know about good acoustics and sound systems in performance and worship spaces.”
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