Book Review: The State of Hollow State Audio in the Second Decade of the 21st Century

February 26, 2020 | 00:00
Book Review: The State of Hollow State Audio in the Second Decade of the 21st Century
Book Review: The State of Hollow State Audio in the Second Decade of the 21st Century
The things likely to strike any reader or potential buyer of this book are (1) the extremely long title and (2) the term ‘Hollow State'. Fortunately, the book cover helps to identify the subject at a glance by showing four large vacuum tubes (Br.E. ‘valves’), one of which is in brilliant focus to reveal its shiny glass envelope, internal structure and, importantly, the glowing filaments. The warm glow is also seen in the tubes that are out of focus.

I showed the book to various people and found that both the title and the cover image provide perfect triggering results like “what’s hollow state?” (from newcomers) and “is that an 807 there and 6AQ5’s in the background?” (from tube aficionados). We’ll see if both camps are served by the contents of the book.

‘Hollow State” begs elucidation to everyone not inside the ‘tube scene’ and I was surprised to notice that the author does not consider this nice coinage worth explaining in his book, but then the term may better known in the US than in Europe. If you are old enough to remember the term ‘(all) solid state’ proudly printed on your portable radio, alarm clock or tape recorder, then ‘hollow state’ makes sense as it refers to the (near) vacuum that exists in, ermm, vacuum tubes a.k.a. thermionic valves! In plain terms, 'solid state’ stands for the transistor, which in the US slowly killed the vacuum tube starting around 1955 and ending some time the future, hopefully.

Once upon a time

In Chapters 1 and 3 Richard Honeycutt provides a short history of the vacuum tube proper and its use in now historic and famed commercial radios and amplifiers. While mentioning a few European contributions in Chapter 1, Chapter 2 predominantly covers products from North America, where the vacuum tube flourished commercially much earlier than in Europe, mainly due to radio and TV entering the US household much sooner than this side of te ocean (but we were happy to wait for TV with 625 lines and PAL colour). In many instances where US companies are mentioned having manufactured radios, tubes, components and audio gear, a few interesting lines describe their history, blunders, successes, takeovers etc. Examples include a giant like RCA but also lesser gods like Altec (for ‘alternative technology’). In between chapters 1 and 3, remarkably, is the one that explains the very basics of vacuum tubes, and this is admirably done especially for newcomers. Throughout the book, Honeycutt’s language and use of electronic terms is factual and to the point without missing an opportunity to explain things in a looser way. Arguably though, a chapter of just 24 pages taking you from the basic triode amp to push-pull should be more textbook style than personal anecdote.

Heating up

More advanced theroretical aspects of vacuum tubes are discussed in Chapters 4 and 5 covering preamp design and the art of curve reading respectively. The preamp design chapter is by no means dry, culminating in a real design using a ‘space-charged’ (wow!) tubes type 12EL6 driven by… an opamp. The hybrid design underscores the author’s view that tubes are neither sacred nor complicated to interface to semiconductor devices. This chapter I found one of the best in the book, discussing the ‘starved amplifier’ also known as the ECC8* (US: 12A*/6/7) running off plate voltages like 12 V i.e. so low that even the all-transistor generation of electronicists sees an opportunity to experiment with these “glow-FETs” now available from China and Ukraine. The history of the starved amplifier, coming out of a popular publication essentially, also makes excellent reading and Honeycutt does a good job marrying theory with a spur to start soldering.
Chapter 5 is let down in part by mediocre reproductions tube characteristics, the famous ‘design curves’ designers should be able to read before switching on *any* voltage high or low. Fortunately, there is no need to read exact figures from the old graphs and the intent of the methods outlined by Honeycutt is clear for the purpose of his discussion.

The “TS” and “OT” words

Chapter 6 covers the “tube sound” briefly and — fortunately for me — avoiding the rhetoric, sheer subjectivism and harsh personal slants so often seen on forums for audio aficionados. Instead, Honeycutt limits himself to discussing the parameters that go into sound perception and the fallacies of giving verdicts on “the best amplifier sound”. The book rightly does not enter the divide that seems to exist between tube lovers and tube haters on the one hand, and further down the line, tube-X lovers and tube-X haters on the other.

The output transformer, the second most dreaded aspect of tube amplifiers after “them high voltages”, gets a rather short discussion in the book in Chapter 9, which only at the end mentions the toroid while skipping the best OT of all times: none! (in Philips Netherlands’ famed 800-ohm OTL design).

The tube surroundings

Further chapters in the book cover not only the usual subjects associated with vacuum tubes like guitar amplifiers (specifically distortion, fuzz, etc.), tube selection, tube testers, power supplies (fighting the hum) and faultfinding, but also rarer phenomena like tubed, tubed microphones and dynamics processing with tubes. The coverage of tube amplifier repair and faultfinding with care is very well presented, full of sincere advice and proof that Honeycutt has been there.


The book sets a standard for its typesetting of formulas and accurate use of italics, super- and subscripts in technical terms and as such imparts good authority. It is slightly let down though by the print quality of some of the illustrations, particularly ‘scope images, some line art and graphs, whose S/N ratio would have improved significantly if passed through the Elektor drawing department. This should not be taken to not apply to the reproductions of vintage amplifier designs though, which have their charm and are not intended for replication.

The book reads smoothly and is well organized with the historic aspects of the vacuum tubes always in the background but not romanticizing or mythizing the past. The book constantly presents a forward looking, challenging view and in some cases prompting you to switch on the solder iron and start experimenting with hollow state devices. State: ready.

Warmly recommended.
The State of Hollow State Audio - in the Second Decade of the 21st Century
Richard Honeycutt
382 pages, soft bound
Elektor International Media
ISBN: 978-1-907920-79-0
Price: €31.46 (Non Members: €34.95), E-book: €26.95 (Non Members: €29.95)

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